Account not working on one computer with thunderbird, but it works on second

Hi, I ran into a strange problem. In my company we all use private server. On one of the computers (Winy 7) suddenly one email account stopped working. After deleting it and trying to add account once again Thunderbird informs me that username and password is wrong. We've checked the settings and everything is the same in comparison with other computers with thunderbird. We've also created a new account to dismiss the possibility of server-side issue. None of it worked. On the other note, on this problematic computer it is possible to configure and use email account on different server.