Hi compaqdrew, I too had issues when I first installed Leopard a week or so ago. Once I disabled the onboard dual lan controller and deleted the forcedeth.kext most of my lock-ups disappeared too. I've also disabled any kind of over-clocking to further increase stability. So far these past few days have been fairly rock steady.

Edit:
I forgot to say that my board is an MSI K9N Sli with the nForce 570 chipset. I'm running an 8600GTS as well as an Athlon X2 6000+

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MacBook Pro 15" | Mac OS X 10.6 • 2 GHz Intel Core Duo • 2 GB DDR2-667 • ATI Radeon Mobility X1600 128 MB • 100 GB Serial-ATA
Hackintosh | Mac OS X 10.5.6 • 3 GHz AMD Athlon 64 X2 6000+ • MSI K9N AM2 • 2 GB DDR2-667 • NVIDIA GeForce 8800 GT 512 MB • ALC888 Audio • 300 GB Serial-ATA
iPhone 3G • 8 GB