Here's a link to a post that addresses this problem:
http://forum.ppcgeeks.com/showthread.php?t=41385
Also check out
http://forum.ppcgeeks.com/showthread.php?t=44583 'Touch Pro Cleanup'.
And it sounds silly, but if you still have on the static cling screen protector it came with out of the box - punch a hole in the earpiece area (or take it off).