Back when I started, I had 1000 weight, and would notice backlinks picked up for me in MSN, etc. Now I have 4000 weight, and no backlinks in MSN, Yahoo, etc? A couple days ago I switched out to an ad with a unique anchor text, and still no backlinks with that anchor text. My stats show nothing as well. I used to have a couple dozen backlinks picked up with 1000 weight, but now I have nothing with 4000 weight? Did MSN stop showing the links or something?
I know it seems like a daft question but did you hit the individual enable links on each keyword (its happened many times) Otherwise check your new stats as they will also tell you how many times your ads have been shown. I wouldnt rely on the SE's to tell you as they don't report all links.
I've got the enable hit on only 1 of my ads - so that it has 100% of weight. No backlinks showing up in either MSN or my stats.
Stats will have a slight delay and will not be totally accurate right away (people switching over, etc). Personally, I have found MSN to suck with reporting backlinks lately. They show a tiny fraction of what other SE's do. I know others have had better luck then I have with that, but i don't think they are showing all of them anymore.