well I'd advise you to disable hyperthreading, you may be suffering from too many threads, I know it sounds strange, but I've seen it a couple of times before.

the -g will help for sure, it fixed many issues for me. There are some other problems with sql 2005 that can affect the size of the proc cache, I advise you to get to sp2 release 3186 as a minimum as I know this fixes some memory allocation " bugs" . Likewise there are some fixes which apply to the o/s if you're not at w2k3 sp2 I'd suggest you get to there too. I'm going to be posting some rdl's to my web site which I use for monitoring sql server, hopefully before christmas, I don't really want to start posting scripts here as it gets messy and some are quite complex.

I'd suggest, as I usually do, that you download an eval of idera sql diagnostic manager and point it at your server ( hopefully you might also buy the product as it really is quite superb and frees up so much DBA time for other more pressing matters ) this will allow you to gather stats, trends and diagnostics.

32bit is really old technology and much like the 640k is enough for anyone, the 2gb limit on 32 bit is in the same vein.