During the course of the day yesterday this happened a number of times. I just waited it out, tried again after 15 minutes and it worked OK.
It is annoying though.
What also bugs me is when I try and open my SPAM folder that has more than 1 page (50)of e-mails in it and the page will not load. It almost looks like the URL string is too long. The warning I get says "This page will not open in IE". I have to go back to the Gmail login and then it opens OK without having to log back in.