PPC - Affiliates - Disaster! Help Needed :(

Hi guys,
I'm totally frustrated with adsense and I will appreciate any help.

Please note, I'm not an adsense beginner, I have a site running for more than a year, yet I can't make it work for me as well as it used to.
I have about 3000-4000 visitors per day, mostly from U.S.A.

I run adsense ads on my site, and some clickbank affiliates.

On December / January I used to make about 23-28 $ per day.
Today I earn about 13$. I made some changes, but I can't really put the finger on what I did wrong. Maybe it's the clickbank affiliates?

First I thought, "oh well, it's the global financial crisis", but than I did a test, I made a roll back to the version of the site of 3 months ago, I had few good days of 20$, so I decided to roll back to the new version, but make the position of the ads excatly as it was 3 months ago.
And guess what? the new version (but with the old ad positions) brought me 25$ for day!!! I thought the problem was solved, but after 2 good days it went back to 13$....

CTR remains the same - about 0.75%, yet ppc went from 0.13 to 0.7.

I think that if I would have to choose the 2 most complicated things in life I would choose Adsense and women.


Now seriously, I'm clueless here.

I won't post my site URL here as I shared the statistics and it will violate their adsense TOS, but if you can help, please PM me and I'll give the info.

Thanks for your time,
Dror.

Oh and of course, I'm willing to pay for any service that will proven as effective.