I'm running (a registered version of) Avira as well, yet with heuristics set to medium level. The number of false alarms has been minimal, and none with PureBasic.
I've had two or three alarms (most notably a 'trojan w32.xxxx.dropper' but the files it triggered on did not cause anything in online virus checkers or another machine where I run a different virusscanner on. Running those apps and checking for spyware (with SuperAntiSpyware, SpyBot, and ZoneAlarm) did not reveal anything so I have to assume they are false alerts as well.
Thus far, I've either been clean for the last 10 years or so (including drive by downloads) in spite of 'risky' Internet and download behaviour

Either that, or none of the scanners I used over time has been working
Typically I run with a real time virus scanner (Avira), a firewall (ZoneAlarm or Comodo), anti spyware (ZoneAlarm, SuperAntiSpyware, SpyBot), on a fully patched and updated machine with many unneccessary services killed.
That approach either works, or I've been the biggest slave of spam networks ever
