CMS 500 Error on CMS if any plugin enabled
 

I'm having a problem with my CMS. It all runs fine except if I enable any plugins. After a time it will start giving 500 errors until I clear the CMS cache.

Does anyone else have or have had this problem and know how to fix it? I have a ticket logged with vb but so far nothing has worked. So I though i would throw it out here.

I have uploaded all files again, and reverted all template mods but it still does it.

Thanks