Clicksor is junk. Try TribalFusion, Casale Media or Burst Media for CPM. You can also try AdBrite, but they don't pay via PayPal, only checks.
Yea, Clicksor is crap. They have viruses too. Casale, Burst, Tribal, Euroclick, Realtech, Adtegrity, Bannerconnect all decent networks with a Paypal option.
The first 2 cpm banner ad networks listed here that are reviewed are the best I have used so far. I use them on my entertainment site. I am getting around $.50 - $.90 cpm currently from the first network listed and around $.35 - $.60 from the 2nd one that is listed. The amount you earn I guess will depend on the type of site you have. All in all, I have 3 banner ads on each page, that's one of each ad format, giving me an average page earning of around $1.65 - $2 cpm. I don't use their popunders, but you can also opt in for them. I prefer not to. Also these are quality networks that do have requirements in place and are used on some larger sites like freeonlinegames.com. I have received earnings from these 2 every month without fail for over 2 years now and even longer than that for one of them. Hope this helps and good luck and hope you had a great Christmas.