Here are the checks you should do yourself to verify what the reason of your weight flux is. These apply to boh people who see BIG drops as well as those who don't revalidate anymore or where weight is 0 now.
- You have read the FAQs and understand how weight is calculated. In particular how it uses the API which often presents different results than Google's public results for the site: command. - When you got the e-mail about your ads being taken out of rotation, you verified that the ads were on the page mentioned in that e-mail. - You verified that all pages within your Base URL have ads showing and all show the same number of ads. - You tried revalidating manually in your account with an API key that you are sure has queries left. - You have verified with an API query (for instance via the Keyword Tracker) that you actually have pages in the Google index. - You are sure you have the latest Ad Network script code running on your pages. - You are sure your server still allows remote file connections so the script can communicate with the ad server. - You have verified that the ad .txt cache file is still writable (CHMOD 777). - You have checked the forums to see there isn't one of the notorious Google updates going on which, if it is, might well be the cause of flux. - You have checked the source code (CTRL + U in FireFox) of one of your pages that displays ads and verified that the output HTML isn't broken. - You have searched the forums for other possible answers already given to people in similar situations. - You checked your referrals and are sure it's not down to one of them loosing weight or abandoning the network.
If you can tick all the above and it's still not working then there's one last thing you can do yourself prior to asking for help. That is waiting for 24-72 hours. Manually revalidate after that period and 9 out of 10 times we see the weight back up. If not, then by all means go ahead and ask here.