In system.log I often find the warning message:
Warning: include(Mage/Enterprise/Pagecache/Model/Observer.php): failed to open stream: No such file or directory
The FPC Module is deactivated within module config xml.
Any one a hint why magento tries to instance it?
Cheers
If your seeing errors like that I would be inclined to ensure the file is actually there - missing core files are not good. You may wish to run a diff comparison between a fresh downloaded copy of the version you are running to see if there are any other files.
As to why its looking for it when it is disabled. When you disabled it (i presume it was previously working or enabled) did you clear the var/cache/ folder it may not have reflected it has been disabled yet.