I've only received that error once last week. Today has been just fine, no errors. I have it open all day long.
I've had it before, but not today and I've been reading/sending emails pretty much constantly all day. The worst one is when you log in and it spews out stream of garbed ASCII. First time I got that I was sure Google beta had corrupted my emails.
I have been seeing this error for past couple of days. When the Gmail was up i recieved this message. 'And we're back again, not that was fast!!' I had a good laugh at this message.
Well, the errors are back today for me. Haven't even been able to login at all for the past 30 minutes.
Next time you can get in, set yourself up for pop3 access - I've never had a problem with that, only with trying to get to the webmail interface.