tried chmod 666, 766, 777 - still get: You must set the ad_network_ads_219.txt file to be writable .
I have tried 755 & 777 on every folder in the file, including the root. I also put ad_network_ads_219.txt in every subfolder and set the same permissions as noted. This is in a wordpress blog. The ad_network_ads_219.php is being found & executed (per the 'make writable' message), but still, can't make the .txt writable.
Found the problem. The .txt filename was missing ..._ads_... in it. Sorry about this fiasco. Thanks for your help! Now I can try & figure out the no validation - seems to be plenty of info here on that.