Thanks again... agreed the rushed bit being large allocations - didn't mean to mis-quote you.
Interesting read on trace flag 7790. I'll have to try this as well (although I'm meant to be spending my time coding not dealing with production issues!!)
I'm also looking at the output from procbuf and this shows some oddities.
Have you seen anything like this...
pbname='Build' pbprocnum=1 pbsharecnt=0 pboldplan=(nil)
<snip>
Total # of PROCHDRs used : 6
Total # of pages used : 84
Total # of bytes used : 160297
Total # of lost bytes for alignment : 15364359
Total # of pages lost for alignment : 7502
Total percentage of memory lost : 9584
More bytes lost than used - Seems odd to me ?
There are some fixes/improvements to procedure cache usage in SP135 - have you tried it yet ?