Hmm, do you overclock??
Getting weird crashes that nobody seems able to fix? Crashes that don't make sense to the professionals?
Watch out for overclocking: two parties who know what they're talking about, and whose jobs include trawling through errors reported via the Error Reporting Tool (yes, those reports you send in when a programme crashes really *are* read and analysed) point to overclocking as causing problems:
Note Raymond Chen's comment that some people did not even realise their CPU's were overclocked.