Thousands of Google email users, Gmail users, are experiencing problems logging into Google. I tried it myself, I am am also receiving 502 errors.
There are huge threads at Google Groups with users complaining as early as 5:20am EST (about 40 minutes since this post).
This is an all too familiar error for these users:
It seems like checking email via IMAP or POP is also having issues. So, I guess the solution is wait for Google to fix it.
This is not the first time Gmail has gone down for the masses. This is the third major one we reported. The last major one, that I remember was on August 11, 2008.
Update: IMAP does seem to be working sporadically for some users.
Update 2: At about 6:15am (EST) some people are beginning to access part of Gmail. Google must be working on it right now. Hopefully it will be fixed shortly.