Are you certain this is the exact error message you're getting? I've yet to see it. It seems that you are modifying a record when the wifi connection drops. Then when you're reconnected FM sees the second connection as a new user. The record is being edited by the first "user" and as such is not available to the new "user". When FM Go reconnects via 3 G are you required to log in again?
Once again, can't edit a post on an iPad. You were clear that you didn't need to reauthenticate.