Keyword Tracking Problem

MSN is using my ad URL, instead of the Keyword URL

[aruns]

I have setup ad & keyword tracking URL, but my network's stats shows only my ad URLs & not my keyword URLs. It looks like Adcenter is not using my keyword url to send traffic.

My urls are setup as follows
Ad URL
www.example.com/?adgroup=adgroup

Keyword URL
www.example.com/?keyword=abc+key+phrase

Am doing something wrong?

Thanks for the help