I assure you there is nothing wrong with the forum. As with most IT issues... user error. 😉
I would usually agree with you but I had to come up with my 5th password when I tried to login ! It will take the new word for 5/6 times then I'll have come up with a new one! OH well
I'm just guessing here mind you but, what it sounds to me someone has hacked your PC and has got your password to this site and keeps changing it to screw with you. Or maybe a friend with a sad sense of humor.
May have others, don't know. Do you have a anti-virus program that covers intrusions etc.and is it up to date?