Thanks for your feedback.
Your temps seem good. I always ask because it's something we all neglect to check and it's the first thing to keep in mind.
Your set up seems rather good too, but is your psu and rail voltages any good ? I'm sure the problem isn't there but keep that in mind as well for general system stability.
I don't use upay myself, but could you back-up your local save game files and config. files (or .xml) as well ? Then delete the original folder/ files and start a new game so that new local config. files will be created. That way your game sees your new card and is configured accordingly. Usually the files i am talking about are located in your documents folder. If not, google it and find out. A game reinstall should not be necessary.
If anything goes wrong, use the back-up files and copy paste them in the default location so everything is at least as it was before.
I assume you have the latest game patches as well.
You can always try an older catalyst driver suite.
Test a little and post your results.
Hope everything goes well. It really is a very good card you've got there.
gigabyte X58A-UD3R rev.2, core i7 975 3.9ghz (stock voltage), windows 8.1 64-bit, corsair 12gb DDR3 1600mhz 7-7-7-20 RAM, xfx HD 5970 + gigabyte HD 5970 (950mhz/ 1100mhz), coolermaster ultimate 900w PSU.
AMD Catalyst 15.4 beta