Hi it seems the issue is with wp-super-cache and nothing to do with your plugin ??
although i did notice this error in the log that you might want to check:
Sat Mar 28 10:57:26 2009] [error] [client 91.124.169.116] PHP Warning: get_browser() [function.get-browser]: browscap ini directive not set in /home/qbrushes/public_html/wp-content/plugins/head-cleaner/head-cleaner.php on line 727