Problems with login

[stunod]

Ok, I have my forum where for years every one of my members have been able to login into their account. I have just converted my site from 3.8 to 4.0 and uploaded the user database.

Some of the users are able to login including me but most of them it tells them that either their username or password is to correct, but I know it was cause I have even tried to change it in the admin control panel.

After messing around with it for sometime I figured out that one of my admins accounts that were locked out for some reason was able to log into my account on the same pc the blocked his account.

Weird??? Yeah but now I have decided to start over with the whole thing and one of the problems I have already is that you can't login to the forum in iexplore but you can in firefox and chrome. I have no idea on what is going on with this at all. I was hoping someone else had one of the two problems and would tell me how they fixed it!

Oh yeah, the new forum is a fresh install with no mods at all.

Thanks,
Adam