Firefox won't start gmail in windows

[mike havens]

it tells me:
     We're sorry. It seems there is a problem. Please try using Gmail
     with a supported browser. If you're encountering this error while
     using a supported browser, we suggest alerting your Internet Service
     Provider (ISP) that a proxy is failing to accept cookies on HTTP redirects.

I know it's not the ISP because my dad's firefox will load it. What
can be the problem? (i know... window's stinks--- the computer is SLOW
now)
-- 
:-)~MIKE~(-: