Fatal error after deactivation/ reactivation

Hello, I had a different error with the Word Press 3.5 update. I deactivated all of my plugins, and the error resolved. At the time of Deactivation - my appointments plug in was working 100% and it was showing my schedule for January 2013.

Now, when I reactivate, it only semi-works (works on the front end for clients, not on the back end) and shows the month of Feb only, not January.

I also get this error if I try to go to the settings and make changes.

Fatal error: Out of memory (allocated 31719424) (tried to allocate 20 bytes) in /homepages/5/d90567736/htdocs/hautecakes2011/wp-admin/includes/misc.php on line 284

Please advise...thank you!