Just spent three months figuring out a problem so I thought I would share it to save someone out there the trouble.
We acquired 2 off the shelf Dell 3100's, P4 3ghz, 2gbs of ram as a second Giga studio system. We used memory configuration 2 which gave us 950mbs of useable ram which was fine. When we started loading pperformances created on another system we got memory errors at around 28%. Really weird. Even weirder was that we could manually load the samples in up to 60%. Save the performance, reload it, same thing happened.
When we reverted to the defaul Windows XP config we only get 25% of useable ram BUT...some of the samples that wouldn't load before did now until the whole thing ran out of memory.
We used his GS Memory optimiser and tried loads of settings. Eventually 80/4000000/0/0 did the trick. We don't have huge amounts of ram, 800mbs but its enough to load what we need and out problem is in part resolved.