I'm getting a strange one on hotmail as well, when I actually open an e-mail it opens and then continually reloads it every 2 seconds or so but only in Firefox, IE or Iron work fine. And yes I did try disabling all the add ons and plugins but to no avail. I think it's a java related problem.
Apparently it was caused by a MS hotmail update on the 18/01, the Microsoft hotmail team are aware if it and will fix it before FF4 goes to RC at the end of February.