Log In Problem

Hi Guy's
Not sure if this is browser cookie related or not but I seem to be having problems signing into my forum, I am the board founder and what happens is when I try and log into the forum on IE6 and Firefox I often get reverted back to the login page, so I clear my browsers cache and login first time, is this a sessions issue of a cookies issue, and how can I solve it?
IM1.40 php4 mysql4
Not sure if this is browser cookie related or not but I seem to be having problems signing into my forum, I am the board founder and what happens is when I try and log into the forum on IE6 and Firefox I often get reverted back to the login page, so I clear my browsers cache and login first time, is this a sessions issue of a cookies issue, and how can I solve it?
IM1.40 php4 mysql4