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The rest of my post is partly speculation... I believe AOL has a few small differences in requirements for ads that google adwords may not. Whether AOL reviews each ad or not, however, I am uncertain. Perhaps they take longer to review ads? Or perhaps you violated one of their automatic checkers by the change without realizing it?
I have also had this happen with some of my ads. While most remain on AOL, some have disappeared. AOL must have turned them off for whatever reason... I will have to look into it further to find out for sure. In the meantime I suppose you could _try_ to email AOL, but response there is probably less likely.