Can login in to Drupal 5.1 site on one machine but not on another?

I don't have a lot of information on this problem. If someone can point me to where I can look for more information I will post it. I'm not even sure if this is the right place to post it but I did post it in a Launch pad forum for Firefox.
Here is the problem.
Two systems each with firefox and the same plugins installed. One runs on Linux Ubuntu 7.04 and the other one runs on Windows XP.
Both firefox version are 2.0.0.6
The system running windows can login with no problems.
The system running Linux Ubuntu 7.04 logins, takes about 1 min and then goes to a totally blank page. No menu, no content, no code
Downloaded Firebug and nothing comes up as code at all.
I could access the site about a week ago and suddenly nothing. I'm a newbie to Ubuntu as well. I have a feeling that the something upgraded in the Linux version of firefox but no clue as to where to look.
Anyone else suddenly experience this?
Thanks
Paulos