It was discovered during FA beta that the direct cause of the problem is LVPrcInj.dll. People found that merely killing this process in the Task Manager would allow them to load up the game. In fact, just renaming LVPrcInj.dll to LVPrcInj.old fixed the problem completely.
Unfortunately it was also discovered by googling this DLL that hundreds of other programs are affected badly by it, and it is very much Logitech's problem that GPG cannot fix without their help.
This DLL, by the way, is used primarily for the "video effects" feature of the webcam, which is of questionable value. If you never use this feature, then you won't notice any difference in how the webcam works and do not have to uninstall it.