I am in Australia. This began happening to me as soon as Yahoo 7.5 came out. Not only did it hit that version, it also struck my Microsoft Messenger. It is really annoying. I haven’t been able to use my cam at these services for weeks. As a work around, if you really want to reach someone, try EyeballChat, which still seems to be working fine.
Thanks for any help you can give, but you are wrong about anti-virus programs. While they do not directly control the software, they often cause conflicts that cause software to malfunction. I have lost count of the number of times i have heard complaints after people have installed anti-virus software that other programs won’t work.