Issue 1:
Following behaviour:

import pandas as pd
# version '0.12.0'
!wget -O 'Vertikale_Netzlast_2013.csv' 'http://www.50hertz.com/transmission/files/sync/Netzkennzahlen/Netzlast/ArchivCSV/Vertikale_Netzlast_2013.csv'
df = pd.read_csv('Vertikale_Netzlast_2013.csv', header=6, sep=';', parse_dates=[[0, 1]], index_col=0, na_values=['n.v.'])
df.rename(columns={'Unnamed: 3': 'Load'}, inplace=True)
df.Load = df.Load.interpolate()
df.count

shows me, that everything is pretty ok:

<bound method DataFrame.count of <class 'pandas.core.frame.DataFrame'>
DatetimeIndex: 35044 entries, 2013-01-01 00:00:00 to 2013-12-31 23:45:00
Data columns (total 2 columns):
bis 35044 non-null values
Load 35044 non-null values
dtypes: float64(1), object(1)>

But when I try to plot it with df.Load.plot() I get the error message:

---------------------------------------------------------------------------
AssertionError Traceback (most recent call last)
<ipython-input-431-abfff097d131> in <module>()
----> 1 df.Load.plot()

/Library/Python/2.7/site-packages/pandas/tools/plotting.pyc in plot_series(series, label, kind, use_index, rot, xticks, yticks, xlim, ylim, ax, style, grid, legend, logx, logy, secondary_y, **kwds)
1728 secondary_y=secondary_y, **kwds)
1729
-> 1730 plot_obj.generate()
1731 plot_obj.draw()
1732

/Library/Python/2.7/site-packages/pandas/tools/plotting.pyc in generate(self)
854 self._compute_plot_data()
855 self._setup_subplots()
--> 856 self._make_plot()
857 self._post_plot_logic()
858 self._adorn_subplots()

/Library/Python/2.7/site-packages/pandas/tools/plotting.pyc in _make_plot(self)
1242 lines = []
1243 labels = []
-> 1244 x = self._get_xticks(convert_period=True)
1245
1246 plotf = self._get_plot_function()

/Library/Python/2.7/site-packages/pandas/tools/plotting.pyc in _get_xticks(self, convert_period)
1032 x = index._mpl_repr()
1033 elif is_datetype:
-> 1034 self.data = self.data.reindex(index=index.order())
1035 x = self.data.index._mpl_repr()
1036 else:

/Library/Python/2.7/site-packages/pandas/core/series.pyc in reindex(self, index, method, level, fill_value, limit, copy, takeable)
2644
2645 # GH4246 (dispatch to a common method with frame to handle possibly duplicate index)
-> 2646 return self._reindex_with_indexers(new_index, indexer, copy=copy, fill_value=fill_value)
2647
2648 def _reindex_with_indexers(self, index, indexer, copy, fill_value):

/Library/Python/2.7/site-packages/pandas/core/series.pyc in _reindex_with_indexers(self, index, indexer, copy, fill_value)
2648 def _reindex_with_indexers(self, index, indexer, copy, fill_value):
2649 new_values = com.take_1d(self.values, indexer, fill_value=fill_value)
-> 2650 return Series(new_values, index=index, name=self.name)
2651
2652 def reindex_axis(self, labels, axis=0, **kwargs):

/Library/Python/2.7/site-packages/pandas/core/series.pyc in __new__(cls, data, index, dtype, name, copy)
490 else:
491 subarr = subarr.view(Series)
--> 492 subarr.index = index
493 subarr.name = name
494

/Library/Python/2.7/site-packages/pandas/lib.so in pandas.lib.SeriesIndex.__set__ (pandas/lib.c:29541)()

AssertionError: Index length did not match values

But index as well as Load got 35044. Bug?

Issue 2:
I have what appears to be a valid Series with a time series index as follows:

In [41]: inactive
Out[41]:
2010-06-10 20:43:07 37.2
2010-06-21 06:37:28 0.0
2009-07-20 06:53:38 0.0
2012-05-17 01:50:13 27.4
2009-07-27 21:09:15 0.0
2010-05-04 09:06:54 0.0
2010-05-06 03:38:54 32.5
2010-05-09 08:33:16 56.9
2010-05-26 18:58:42 0.0
2010-05-31 18:40:41 0.0
2010-06-13 08:46:17 0.0
2010-06-16 18:27:51 0.0
2010-06-19 11:59:48 0.0
2010-06-24 15:24:26 33.4
2010-06-28 10:54:27 0.0
...
2008-11-02 07:35:22 71.2
2008-11-05 17:33:39 97.6
2009-10-22 23:15:39 75.7
2009-10-27 20:55:07 67.5
2009-06-02 13:57:15 35.8
2009-06-06 14:15:41 25.9
2008-11-07 01:22:46 0.0
2009-10-12 17:08:20 100.0
2010-09-19 10:21:39 0.0
2010-09-24 15:46:50 0.0
2010-09-30 16:48:09 0.0
2010-10-08 21:43:10 0.0
2010-10-15 19:27:11 0.0
2010-10-28 19:10:42 0.0
2010-06-13 10:32:45 100.0
Name: pdgt10, Length: 13536, dtype: float64

Note also:

In [43]: inactive.isnull().sum()
Out[43]: 0

In [45]: inactive.index.size
Out[45]: 13536

In [46]: inactive.values.size
Out[46]: 13536

However, when I try calling inactive.plot() in order to get a time series plot, I receive a puzzling AssertionError:

In [40]: inactive.plot()
---------------------------------------------------------------------------
AssertionError Traceback (most recent call last)
<ipython-input-40-cdcfa4d871e5> in <module>()
----> 1 inactive.plot()

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/tools/plotting.pyc in plot_series(series, label, kind, use_index, rot, xticks, yticks, xlim, ylim, ax, style, grid, legend, logx, logy, secondary_y, **kwds)
1730 secondary_y=secondary_y, **kwds)
1731
-> 1732 plot_obj.generate()
1733 plot_obj.draw()
1734

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/tools/plotting.pyc in generate(self)
856 self._compute_plot_data()
857 self._setup_subplots()
--> 858 self._make_plot()
859 self._post_plot_logic()
860 self._adorn_subplots()

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/tools/plotting.pyc in _make_plot(self)
1244 lines = []
1245 labels = []
-> 1246 x = self._get_xticks(convert_period=True)
1247
1248 plotf = self._get_plot_function()

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/tools/plotting.pyc in _get_xticks(self, convert_period)
1034 x = index._mpl_repr()
1035 elif is_datetype:
-> 1036 self.data = self.data.reindex(index=index.order())
1037 x = self.data.index._mpl_repr()
1038 else:

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/core/series.pyc in reindex(self, index, method, level, fill_value, limit, copy, takeable)
2649
2650 # GH4246 (dispatch to a common method with frame to handle possibly duplicate index)
-> 2651 return self._reindex_with_indexers(new_index, indexer, copy=copy, fill_value=fill_value)
2652
2653 def _reindex_with_indexers(self, index, indexer, copy, fill_value):

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/core/series.pyc in _reindex_with_indexers(self, index, indexer, copy, fill_value)
2653 def _reindex_with_indexers(self, index, indexer, copy, fill_value):
2654 new_values = com.take_1d(self.values, indexer, fill_value=fill_value)
-> 2655 return Series(new_values, index=index, name=self.name)
2656
2657 def reindex_axis(self, labels, axis=0, **kwargs):

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/core/series.pyc in __new__(cls, data, index, dtype, name, copy)
491 else:
492 subarr = subarr.view(Series)
--> 493 subarr.index = index
494 subarr.name = name
495

/Library/Python/2.7/site-packages/pandas-0.12.0_80_gfcaf9a6_20130729-py2.7-macosx-10.8-intel.egg/pandas/lib.so in pandas.lib.SeriesIndex.__set__ (pandas/lib.c:29092)()

AssertionError: Index length did not match values

As I have shown above, my index length and my values are the same length.

Running a recent (<2 weeks) build from master on OS X 10.8.4 and Python 2.7.2.