[HTC One S] tim_h:
Damn, it happened again. It worked flawlessly for some hours. I was then inside a WiFi. When I left and switched WiFi off, it did not reconnect to mobile data and hasn't since then (I have driven 20 km, so also changed cellphone towers).

I looked into the logcat and think I located the part where this happened. I highlighted some relevant lines. Maybe it helps to diagnose the problem? It says something with "apn failed" in there. But the apn settings worked a few hours ago.

Damn, this could be a show-stopper for me ... any help would be greatly appreciated!

WifiService	655	[COLOR="Red"]setWifiEnabled: false[/COLOR] pid=883, uid=10008
04-11 17:00:53.301	D	ConnectivityService	655	ConnectivityChange for WIFI: DISCONNECTED/DISCONNECTED
tryFailover: set mActiveDefaultNetwork=-1, prevNetType=1
04-11 17:00:53.311	D	ConnectivityService	655	[COLOR="Red"]Attempting to switch to mobile[/COLOR]
Attempting to switch to BLUETOOTH_TETHER
04-11 17:00:53.321	D	MobileDataStateTracker	655	default: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=default
[COLOR="Red"]default: Received state=CONNECTING, old=DISCONNECTED, reason=dataEnabled
default: setDetailed state, old =IDLE and new state=CONNECTING[/COLOR]
04-11 17:00:53.331	D	MobileDataStateTracker	655	fota: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=fota
fota: Received state=DISCONNECTED, old=DISCONNECTED, reason=dataEnabled
04-11 17:00:53.341	D	MobileDataStateTracker	655	dun: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=dun
dun: Received state=DISCONNECTED, old=DISCONNECTED, reason=dataEnabled
supl: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=supl
supl: Received state=DISCONNECTED, old=DISCONNECTED, reason=dataEnabled
04-11 17:00:53.351	D	MobileDataStateTracker	655	hipri: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=hipri
hipri: Received state=DISCONNECTED, old=DISCONNECTED, reason=dataEnabled
ims: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=ims
04-11 17:00:53.351	D	ConnectivityService	655	resetConnections(wlan0, 3)
04-11 17:00:53.351	D	MobileDataStateTracker	655	ims: Received state=DISCONNECTED, old=DISCONNECTED, reason=dataEnabled
mms: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=mms
04-11 17:00:53.361	D	MobileDataStateTracker	655	mms: Received state=DISCONNECTED, old=DISCONNECTED, reason=dataEnabled
cbs: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=cbs
cbs: Received state=DISCONNECTED, old=DISCONNECTED, reason=dataEnabled
04-11 17:00:53.471	D	Nat464Xlat	655	requiresClat: netType=1, hasIPv4Address=false
04-11 17:00:53.471	D	MobileDataStateTracker	655	default: setPolicyDataEnable(enabled=true)
04-11 17:00:53.471	D	ConnectivityService	655	handleInetConditionChange: no active default network - ignore
04-11 17:00:53.481	D	MobileDataStateTracker	655	default: setPolicyDataEnable(enabled=true)
04-11 17:00:53.501	D	MobileDataStateTracker	655	default: setPolicyDataEnable(enabled=true)
04-11 17:00:53.651	I	ActivityManager	655	Delay finish: com.amazon.venezia/.StartupReceiver
04-11 17:00:53.661	I	ActivityManager	655	Resuming delayed broadcast
04-11 17:00:53.801	I	ActivityManager	655	Delay finish: com.amazon.venezia/com.amazon.mas.client.tokenrefresh.RefreshScheduleReceiver
04-11 17:00:53.821	I	ActivityManager	655	Resuming delayed broadcast
04-11 17:00:53.831	I	ActivityManager	655	Start proc com.h9kdroid.multicon for broadcast com.h9kdroid.multicon/.MasterReciver: pid=9630 uid=10105 gids={50105, 3002, 3001}
04-11 17:00:53.921	D	MobileDataStateTracker	655	default: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=default
04-11 17:00:53.931	D	MobileDataStateTracker	655	default: Received state=CONNECTING, old=CONNECTING, reason=(unspecified)
04-11 17:00:53.971	I	ActivityManager	655	Start proc com.android.settings for broadcast com.android.settings/.widget.SettingsAppWidgetProvider: pid=9647 uid=1000 gids={41000, 1028, 1015, 3002, 3001, 3003}
04-11 17:00:54.211	W	ContextImpl	9647	Calling a method in the system process without a qualified user: android.app.ContextImpl.bindService:1590 android.content.ContextWrapper.bindService:517 android.bluetooth.BluetoothInputDevice.doBind:256 android.bluetooth.BluetoothInputDevice.<init>:249 android.bluetooth.BluetoothAdapter.getProfileProxy:1198
Calling a method in the system process without a qualified user: android.app.ContextImpl.bindService:1590 android.content.ContextWrapper.bindService:517 android.bluetooth.BluetoothPan.doBind:148 android.bluetooth.BluetoothPan.<init>:141 android.bluetooth.BluetoothAdapter.getProfileProxy:1201
04-11 17:00:54.221	W	ContextImpl	9647	Calling a method in the system process without a qualified user: android.app.ContextImpl.bindService:1590 android.content.ContextWrapper.bindService:517 android.bluetooth.BluetoothMap.doBind:109 android.bluetooth.BluetoothMap.<init>:102 android.bluetooth.BluetoothAdapter.getProfileProxy:1213
Calling a method in the system process without a qualified user: android.app.ContextImpl.bindService:1590 android.content.ContextWrapper.bindService:517 android.bluetooth.BluetoothPbap.doBind:164 android.bluetooth.BluetoothPbap.<init>:157 com.android.settings.bluetooth.PbapServerProfile.<init>:68
04-11 17:00:55.082	D	[COLOR="Red"]MobileDataStateTracker	655	default: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=default
default: Received state=DISCONNECTED, old=CONNECTING, reason=apnFailed
default: setDetailed state, old =CONNECTING and new state=DISCONNECTED[/COLOR]
04-11 17:00:55.082	D	ConnectivityService	655	ConnectivityChange for mobile: DISCONNECTED/DISCONNECTED
Attempting to switch to WIFI
Attempting to switch to BLUETOOTH_TETHER
04-11 17:00:55.082	D	Nat464Xlat	655	requiresClat: netType=0, hasIPv4Address=true
04-11 17:00:55.092	D	MobileDataStateTracker	655	default: setPolicyDataEnable(enabled=true)
04-11 17:00:55.112	D	MobileDataStateTracker	655	default: setPolicyDataEnable(enabled=true)
04-11 17:00:55.573	D	MobileDataStateTracker	655	default: Broadcast received: android.intent.action.ANY_DATA_STATE apnType=default
default: Received state=DISCONNECTED, old=DISCONNECTED, reason=(unspecified)