Console errors when file upload fails

Trying to upload an additional revision to a document and the upload hung

![screen shot 2014-01-10 at 11 41 19 am](https://f.cloud.github.com/assets/1731910/1889133/d15c0e30-7a16-11e3-8ae5-5615e644bfe3.png)

Errors in console:

![screen shot 2014-01-10 at 11 47 35 am](https://f.cloud.github.com/assets/1731910/1889144/f331a380-7a16-11e3-9871-c0d7a72ddb16.png)

Note that first revision to the same document worked fine.