Cookies problem and LOGIN-problem

i have a nonpublic weblog, i know the passwords of some of the subscribed persons. when i give in THEIR username and passwords I can login into antville, but NOT into my WebLog. From my PC i can only login into my log with my username and password. apart from that the cookie function has already for weeks stopped to exist, which means that the computer does not remember my usual login. is it a prob of my home pc, that it does not accept other usernames than my most used one? i run the risk of losing subscribers: they cannot read the log, even when they are members of the site: in their profile stands that they are subscribed to it: they always get the members/login page and nothing else. ws.