You may have a bad or missing account in a transaction. Try to find the transaction and change the account to the correct one. See Error 63; ACT2.dat problem. Before following those steps, it is good practice to backup your data.

You mention this happens when entering a Payee to post a transaction. Select Transactions | Automatic Entries for that Payee and make sure there are valid accounts on the Multiple Distribution screen.

Another take on the problem and solution is at Error 63 . That post suggests using Test Mode and Rebuild Chart of Accounts Files. Do this only as a last resort, since it resets all you customized Category names. Be sure to back up first.

- David
FNI Technical Support
Case #38-10984