Yesterday I heard a couple of people over twitter and many other places saying that Gmail Apps has some problem while logging in the account and faced a 502 server error. Luckiliy Google Apps was the one which showed me the path.
Google Apps Discossuin group is running a thread on 502 Server Error on my Google Apps Email account ? which has been answered by one of the Google Apps Advisor , Mark who said
A small subset of our users are experiencing this issue, and our
technical team is currently working to resolve this issue.
We will provide an update here when this issue is resolved.
It seems some set of users are affected so in case you are the one keep track here and dont worry about your data. Google wont loose it.