I had a local folder with several tasks inside and chose "Actions->Synchronize Todos in Account". Afterwards account was lost, also did not came back after a `akonadictl restart` and restart of tasks-mobile. Fortunately, I have not been able to reproduce. Observed in 4:4.5~20100922.1178352-1maemo1.1177763 .
Can you try again, please? Haven't seen a behavior like that at all...