IMO, your upgrade install screwed something up.... Chasing down those patches and doing tweaks are more than not likely to fix your problem.
If it were me, I'd find some time and do a clean uninstall of X1 and X2 (everything, incl. registry entries), and then do a clean install of X1, then X2 (or just do X2, if you feel particularly brave).
Do you use backup imaging (ie. True Image, Paragon Backup, Win7's built in uility, etc)? Your situation is a perfect example why one should always have the ability to "go back" to a safe point if an install/upgrade goes south. (I can recommend Paragon's free version, which I've been using for about 2 years with no problems whatsoever).
BTW, I can add myself to the list of users who installed X2 without any issues. (It should be mentioned that I completely removed X1 first, as I am just a hobbyist and was in-between projects -- which made it a fairly easy decision for me).
Good luck, whatever you do, and keep us posted.