Since you do have a dedicated server, I went ahead and removed the Apache RLimits for memory completely. This should give your PHP applications the full 64M that is set in the php.ini. If you do need us to increase the PHP memory limit let us know, however, I do not believe this will be necessary. The reason I say this is because PHP5 uses about 20+M of memory itself. With the Apache RLimits in place, this restricts the amount of overall RAM allocated to the PHP processes. With the RLimits removed, it will give PHP all the memory it needs until PHP itself hits the PHP memory limit.
I'm not a tech guru but it seems like the problem is fixed.