occasional clicks question

I now use Sonar 3 with an audio delta M card on a highly powerful computer and the sound is great. However, I think I need to do some tweaking. It doesn't appear to be directly due to the soundcard's settings generally within Windows XP because I don't get any clicks when I record in Soundforge, but the occasional click does come up when I'm multitracking in Sonar. I've tried various things within Sonar already including a rather haphazard series of changes to latency, but nothing eliminates clicks entirely.
Any ideas for tweaking would be gratefully received.
In case you need to hear the clicks (and they are rare, but just enough to spoil a recording) have a listen to my recordings of Diaries of a Tarot Player, Ave Verum, Sing joyfully and most particularly Lazy guitar on www.dwsolo.tomptempo.com
As you will hear some of the clicks occur in microphoned tracks and some occur in VST tracks (Edirol, Garritan, Synful).
Another curious and possibly related problem - I sometimes get clicks on my headphones, while I am recording, but these seem to be restricted to the headphones and don't normally go onto the recored tracks. I don't know if there is a connection.

Also - has anyone had such problems and have they simply gone away with an update to Sonar 4???

Thanks for any advice.
David

yes, thanks, I've read those. My situation *may* be different in that it ONLY happens in Sonar (not in other programmes such as Soundforge).
OK it's similar in that the original questioner, like me, has a computer for music only, but unlike me he uses lots of protection software, which I don't need because I'm entirely *offline* on that computer - ie no Zone Alarm, no antivirus, no antispyware , no online stuff whatsoever, because they are not needed.
So any further ideas re anti-pop tweaking in my particular case would be of interest.
The electric supply question (eg fridges swicthing on and off) also seems to be unrelated, because, as I say soundforge is unaffected, only Sonar...
Any other ideas welcome...