Ok there is something wierd going on...there are times on my site adsense appears without any ad clinet id aka publisher id number.
I noticed this when somone linked to my site and i followed that link and then suddenly i noticed advertise on this site link in my adsense block...its very strange cause i disabled the feature and the link stopped showing in my adsense and now it had suddenly appeared again. So i check the adsense code and guess what....no publisher id "google_ad_client = "";"
Even more strange when i click on the advertise on this site link it takes me straight to the adwords signup page not the advertise on this site page.
Obviously this isn't anything to do with Google, as the source code of your pages is incorrect. I can see only two options - A) you are generating the page dynamically and have a bug in your code somewhere which makes it send incorrect adsense code occassionally, or B) you have some weird ad/privacy/whatever firewall/filter which is interfering with the display of your pages.