I have same problem, I don't think it is about the server and time clock. Because:
1- I still can not login into my own Punbb, BUT I can login into here. This is drive me more crazy and confused.
2- I have to use FireFox browser, then I can login into my own Punbb.

    Therefore, I still try to search the help from all of you guy. I think main point is some think in the code of Punbb forum. This is only help from who created this fantastic forum Punbb. I like it a lot, fast and simple control. Thank for Punbb.