Test 5 is very likely your ram, try loosen Trfc.

NB unstable is errors in test 2,3 and 4.

Sometimes tightning up AI clock twister helps even though it sounds odd, try moderate instead of light. (it migth lock up instantly though)

How much volts you're feeding that NB and how hot does it get?

Here's 600FSB, PL 8 and some nice ram frquency and timings --32M proof:



Run is completely untweaked, just stabilty testing.