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...
http://support.apple.com/kb/ht1923
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...
http://support.apple.com/kb/ht2292
or 
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.