An annoying bug that had one developer here tearing his hair out (our would have, had he any) - an ASCX user-control that has been working fine for a few weeks started to cause strange Visual Studio crashes or hangs.
The project compiles - and runs - fine, but if he opens the code in Visual Studio in Design mode (or in Code mode and then switches to Design), the Studio would crash when switching to Code view, or hang when saving.
We tried this on different machines, I tried erasing the code-behind file - no go
When I started going over the ASCX manually, in Notepad (it's a huge ASCX, with lots of different tables that get alternately shown or hidden) I finally spotted the problem - inside a small TD tag somewhere in the middle the text got corrupted - the Style tag had about 8000 spaces inserted between the opening quote mark and the first css attribute - a bit hard to see when you're working without word-wrap and you can't see the end of the line.
Erased it in Notepad and reopened it in VS - works like a charm.
I don't know who to blame for the text corruption - my guess would be Clearcase.
[Update: It seems there's a known bug that causes Visual Studio to corrupt files located in ClearCase views]