I have had numerous issues with Itunes 64 bit 11.1.38 (and other previous versions) locking up and crashing upon start with "Itunes has stopped working" or "R6027 pure virtual function call". I have researched the answers around the forums as well as having tried some extensive and repetitious troubleshooting myself and thought I'd list them here... in order of troubleshooting...
1. Install all Windows updates and reboot. This seems to clear issues from
time-to-time... I suspect Itunes expects the latest-and-greatest as far as
Windows is concerned.. see if this clears your issue.
2. Remove the contents of your "Iphone photo cache" (or other related product) directory...
3. Try editing the shortcut properties and configure the shortcut (for all
users) to run as Administrator.
4. Try editing the shortcut and configure it to run in Compatibility Mode for
Windows 7 (for all users).
5. Uninstall all Itunes and Apple products; reboot, remove their directories, remove lingering Itunes registry entries, reboot again, reinstall using "RUN AS ADMINISTRATOR" to install the Itunes executable. See if this allows Itunes to stabilize. Please be sure to use the following guide from Apple as far as removing the apps and directories are concerned...
NOTE: If you are having issues with accessing ITunes STORE, try reinstalling the latest QuickTime player.
6. a.Try using MSCONFIG to locate a potential conflicting application or
service using the following...
6. b. Remove the last recent software application(s) you may have
installed... in my case removing GREENSHOT http://getgreenshot.org/ stopped my
Itunes from crashing on startup and it stabilized after driving me nuts for weeks.