Help please: "stuttering" IIGS

["Scott V. McGuire" <fake@f.a.k.e.net>]

I've got a ROM 03 Apple IIGs with a Transwarp GS, MicroDrive hard card
and a GS-RAM Ultra memory card.  Today it started "stuttering" by
which I mean working for a bit than freezing for a bit then working
again ... When it unfreezes it seems to respond to buffered key
presses and mouse movements from when it was frozen.  I haven't made
any recent changes.  Has anyone seen this behavior before?  I've
tried: switching keyboards and mice, turning on/off dma on the hard
drive, lowering the speed from 8MHz to 6.25MHz (by changing the
oscillator on the Transwarp GS, reversing a change I made over a week
ago) to 2.8 MHz to 1.0 MHz (via Control Panel).  The problem may have
gone away at 1.0MHz, but the system was so slow that I'm not sure I
could tell - and I didn't leave it at that speed very long.

Help appreciated,
-Scott