How do you completly uninstall uxtheme?
I am not sure if this will work, but maybe you can go start > run > type sfc /scannow
since it's a system file it should see that it's different and replace it with the original (you'll need your winxp cd)
The UXtheme.dll Multi-Patcher, assuming you downloaded from Neowin.Net, "patches" your system, replacing XP's .dll file with it's own version. In the process, it should have re-named the original .dll to "uxtheme.dll.bak"... or as it was explained to me, it should have. At any rate, the Multi-Patcher should present an "uninstall" option if you simply re-run the original executable. Which of course will restore the orginal .dll file of your system.
Regardless, the best place for any information regarding your specific problem, would most likely best be solved at the Neowin.Net forums.