According to Mozilla, it has received "lots of sync complaints around server problems". Accounts cannot be deleted due to a deletion-page error. The company said that it may have "broken the 'reset your sync account' fix as well." Additional issues include an incompatible Yahoo Toolbar in 7.0.1, Yahoo mail errors, Java incompatibilities, as well as AVG anti-virus, which needs to reinstalled manually by users once they upgraded to 7.0.1.
Firefox 7 was a hiccup when it was released, which is a shame since it is the first true rapid release version. Now it seems that Mozilla will be busy fixing Firefox 7.0.1 for a while and that will definitely take its toll on Firefox 8 development. There is no news yet how Firefox 8 may be affected, but we would expect that it could be delayed.
For the current version of Firefox, we recommend not upgrading to version 7 or 7.0.1 just yet.
UPDATE: Mozilla has reached out and clarified the issue surrounding Sync problems: