It happened to me this morning, but worked when I put in this address:

https://mail.google.com/mail

Found it out here

I refuse to continue my workday without it

see, mine doesn't even say "loading..." it's just...not there any more. all i have in the sidebar is my labels.

nevermind! even though i never turned did this, so i'm still not sure why it originally turned off, the answer is here.

I WANT IT BACK.

Man, you and no one else. The jabber server is one thing, but the in-browser crap is, uh, crap.

actually, everyone except you and tommy that i know really likes it. i like having it at the newsroom cause we're unable to download other chat clients (well, i can use aim express but that's a piece of crap).