This started slowly, a couple weeks ago. The only changes I recall between when it worked and when it broke was maybe some Windows Updates. I have no idea which ones. And, of course, automatic database updates to my security suite software.
Windows 7 Home Premium x64. Security is Kaspersky Internet Security version 9, only reason I upgraded from v8 is that 8 is not compatible with Windows 7.
The basic problem is that Windows Explorer (ie, the system shell and file manager) will crash. So far as I can tell, no crash data is being sent back to MS. At least, 99% of the crash dialogs just say "close and restart the program".
This can happen when trying to right-click on something to pull up the Properties or Rename dialog, or any other context-menu command. It can happen when pressing [F2] to rename a file. Depending on exactly where I am in Windows seems to determine if it's just a file-manager explorer.exe process that crashes or the entire GUI. When it's the entire GUI, most of it restarts, but some items sometimes fail to re-show in the Taskbar and/or system tray.
Over all, it does not seem to matter how long Windows has been up, but the longer it is up the more likely it is that it'll crash.
Possibly related to this, is that I cannot use sleep/hibernation. Windows becomes unstable when resuming from sleep or hibernation. I have contacted Microsoft about that and after several weeks of back-and-forth via email and telephone, the problem has been archived as unresolved.