I have been searching this issue for the past 3 days. I cannot update to 10.6.5.
I installed snow leopard 10.6.3 from the retail DVD, and it works flawlessy, even the graphics card now, (haven't tested OpenGL in games but cinebench in games is way smoother than before) I just can't update.

When I try to, it says 'cannot be installed on this disk because an error occurred while evaluating the JavaScript of the package' or whatever. I have reinstalled 3 times, and still no go. I have tried doing it in safe mode, in a different user account, I have tried redownloadibg the update from the mothership site, and same problem,

Anyone else ever get this problem?

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Hack Pro:
AMD Athlon 64 Dual-Core X2 5600+ 2.8GHz
Asus M2N-SLI Deluxe Motherboard
8GB ram (4x2GB DDR2-800)
XFX Geforce GT240 1GB DDR5
500GB SATA HD (Snow Leopard 10.6.6)
250GB SATA HD (Windows 7 64bit)