fatal error on frontpage after installation

hi
i installed sef advanse 2008 on my joomla 1.5 and got this meesage on the frontpage. I cant access it now when sef is enabled
Fatal error: Cannot instantiate non-existent class: jprofiler in /home/digita59/public_html/components/com_sef/sef.php on line 0


anyone seen this before?

got it!
Sakic told me to to try to install on a clean site. I unstalled all components ,then installed sef. now I have to find out which component collides with sef

I got that when ever I turned of the cache of SEF ADVANCE, and have nothing else turned on.