Here are a couple of things to try:
1) try using the DFP 2 Beta Build, it is available in the Beta Builds Section of the DFP Download page.
2) try increasing the memory_limit setting int the php.ini file, try using:
memory_limit = 258M
3) in order for the error reporting code to be effective, it must be at line 1 of your page. move this code:
to line 1.