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#21
If you uninstall all anti cheat tools and it's still not stable then we can look elsewhere. But we (I) can't really do any further troubleshooting with PunkBuster installed. Those System log entries strongly suggest that it may well be having an impact.
I'm only suggesting a temporary uninstall, just to determine whether it is contributing to the problem. If it turns out not to be doing so then you can safely reinstall it. That's cheaper than buying a new graphics card to test.