Running 2.16, I have set up a campaign like so:

So am I correct in assuming that if I pass the "track" parameter to the URL like this:
http://mycpvlabinstall/base.php?c=31&key=f4e3fb5818769d13ca03526b781csec7&track=HelloWorld

Are you seeing that click showing up in your CPVLab statistics at all? That would definitely be the first thing to check.
I take it you copied that URL from the link under "Campaign URL" in your CPVLab campaign setup?
OK - I can't seem to make it work. Maybe there is a BUG in my CPVLab install.
What alternative methods can I use for tracking individual ad clicks?
If I understand CPVlab right you should be able to add custom tokens for the traffic source directly, and you can have the "capture extra tokens" option enabled somewhere.
Yeah, that doesn't work.
Holy shit this sucks, I get conversions flowing in --- but I don't know from which ads! How on earth am I supposed to scale?!
Add this at the end of your campaign url &ad={ADID}
Thanks rondee; I actually have tried that and still see no results. I even tried a clean CPVLab install - same thing.
Here's my work-around... pretty shitty to set up new campaigns like this, but it works...

Have you contacted cpvlab support about this? Sounds like there's something low level and weird going on, and they may be the best people to diagnose that.
I'm on the road at the moment, but will have another look at this when I'm back and have access to my own cpvlab, and see if I can figure out what's going wrong for you.
Thanks a lot caurmen! :-) Looking forward to your reply.
Haven't contacted support yet, but will do asap.
EDIT:
Having researched Prosper202, everything seems to work great there. I think I will switch over for a test run; will take some time getting used to a new tracker, but ... if it works it works