Keep getting incorrect user name/password when logging in

Every time I try to log into my webmail from my computers or iPhone, I get an incorrect user name or password error message and haven't been able to receive my mail in my inbox. The server (Cox Communications) is telling me I need malware or spyware or whatever the heck one uses for this type of thing. I've never had to worry about that before but have recently posted items on Ebay, Craigslist and also a resume online which is about the time I seemed to start having problems with my server connection. Help!

I have a 5s iPhone, an OSX Mountain Lion and a Lion and it is happening on all three devices