Windows 7 Win 7 Thinks Logical Drive is Disconnected Network Drive

The title says it all really - woke up this morning, switched on the laptop, and Windows 7 is showing my logical (D) drive as a disconnected network drive... I can still access it ok, but all shortcuts to any folders in it that are on the desktop now have something (can't make out what) on top of the normal icons - I'm guessing this is due to the fact that it thinks it's a disconnected network drive.

I'm pretty stumped with how to fix this, so am open to suggestions.

Update: It also thinks that any external USB drives connected are disconnected network drives...

TIA