firefox problem

i keep getting an error m,essage about 5 mins after using fire fox on the net its a windows based msg for reporting problems back to microsoft, i says an error occured and it is something to do with firefox.exe and my digital protocol ID
C:\DOCUME~1\LOCALS~1\Temp\WER2B.tmp.dir00\appcompat.txt
that is the directory that the error occured in i just deleted the front bit out of it. please help it have never dont this to me before..