Visual Studio randomly stops responding to mouse clicks and doesn't show tooltips while hovering mouse.
This happens under Windows Vista 64-bit only.
Under Windows Vista 64-bit GetCursorPos API call sometimes fails in 32-bit processes (including Vistual Studio).
See bug description on Microsoft Connect and documentation on GetCursorPos (especially comments)
Upgrade to Windows 7 64-bit, if possible.
For Windows Vista users, we've developed special wrapper for devenv.exe process to fix this function by calling GetCursorInfo instead.
To use the wrapper download JbGetCursorPosFix.zip file, unpack it and run JbGetCursorPosFix_vs* instead of devenv.exe for Visual Studio 2005, 2008, 2010.
This patch is unofficial and is not supported by JetBrains!