I enjoyed the Blue series also, but found they were one brand that caused issues on the main music system here. Wish they didn't but they did, in XP a couple years ago.

May try removing those temporarily (in the FX window is a button to exclude certain plugins, and they can be added again later once removed from the exclude list). May be worth testing.

Is both MIDI and AUDIO stuttering? May be that you need that RAM for the higher end plugins you have. It's pretty inexpensive to add 1 gig to a P4 usually.
What is in there now? A single stick, two sticks? If three sticks we may have found a clue.

I do not work here, but the benefits are still awesome
Make your sound your own!