I do not know what changed on your PC to stop FSBuild from displaying properly all of a sudden. You may see a problem with another program that will give a clue.
Maybe you will see another symptom with another program.
Just to verify .. the version of FSBuild you reinstalled was the one you originally downloaded from SimMarket .. correct?
As a test:
Disable Visual themes
Disable desktop composition
Run FSBuild in "Compatibility Mode"
Did this work?
Lastly:
You could try an FSBuild Update just to see what happens:
http://www.fsbuild.com/dl/Fsbuild2376_2Upd.exe