Lets put some shadow now what actually created a problem from Google's explanation
We released a storage software update that introduced the unexpected bug, which caused 0.02% of Gmail users to temporarily lose access to their email. When we discovered the problem, we immediately stopped the deployment of the new software and reverted to the old version.
Update (3/1/11, 12:20 PM PST):
Data for the remaining 0.012% of affected users has been successfully restored from tapes and is now being processed. We
plan to begin moving data into mailboxes in 2 hours, and in the hours that follow users will regain access to their data. Accounts with more mail will take more time. Thanks for bearing with us.
Update (3/2/11, 10:55 PM PST):
Gmail should be back to normal for the vast majority of people affected by this issue. If you are still experiencing issues, please contact us at the temporary alias we've set up for this particular issue, [email protected]
If any feedback, queries are always welcome!