My most recent episode of hair-pulling involves an older (read: not the most recent) version of Net-SNMP. Halfway through the development of some OID handling scripts, it seemed my code was broken and generated bad results (read: broke the SNMP Get queries). After some trial-and-error, retry-from-scratch, etc steps, I eventually turned on full debugging. A few minutes later I installed the most recent version and a muted Yay! came from my cubicle. Nothing turned up the in bug reports or mailing list so far.
Remember kids, always try the most recent version of your favorite poison, even if it's just a local copy!