Thanks. I'll try tweaking the GTL's now to see if I make any head way.

WEIRD>> my problem of not being able to reboot when setting a value to VTT other than AUTO have disappeared after I set VTT to 1.22. I really have no explanation other than maybe that VTT was stuck at a particular value and I never set it high enough to get it "unstuck".

Anyway, as I'm typing this right now, OCCT is running in the background with the following settings:
RAM/FSB at 1:1 for 533Mhz,
vNB 1.26,
NB GTL .625x,
VTT 1.16,
PLL 1.52,
vDIMM 1.9,

PL 10 (can't go below at 1:1 due to some bug with the BIOS),
Static Read ENABLED
Mem OC Charger ENABLED
AI Transaction Booster MODERATE