I’m guessing people have at least heard of Productivity Power Tools plug-in for Visual Studio. If not, I strongly recommend you give it a shot.
There’s a feature in this plug-in that’ll fix mixed tabs. A toolbar appears on the top that shows three buttons – "Tabify", "Untabify" and "Don't show again" along with the 'x' to close the toolbar. Off-late whenever this toolbar appeared and I clicked on any of the buttons, it did nothing. Clicking on it for the second time, crashed my VS2010. The crashing became more frequent after I installed SP1 for VS2010.
I created a bug for Microsoft on their connect site. I recently got an update from them saying that the issue was fixed and I was told to upgrade my Productivity Power Tools extension.
So if you are on version 10.0.20214.15 AND if you want your Visual Studio to not crash (duh), it’s better you upgrade at least to version 10.0.20318.14.
If however, you want this feature to be disabled permanently (I know sometimes it gets annoying), you can just turn off the Fix Mixed Tabs from Tools –> Options. As it shows, this requires VS to be restarted for the changes to take effect.