If you think an account is wrong check as follows. (If on Professional first run a reindex and data integrity test)
Note that full instructions with pictures can be found in the help files under 'Edit Balances'
1. Recall all archived lines
2. Unmatch all matched lines
3. Check that the match column is blank all through the account - scroll up and down through the lines to ensure there are no matched or archived lines remaining.
4. Go to Account Details and click on the 'Edit Balances' button. This will check that the transactions add up to the totals owing stored on the account and report any differences.
5. If there is a problem - If there is a value under Acc b/f then you can make that =0. Use the left arrow to move all calculated balances in the right hand column to stored on the left. (Full instructions with pictures in the Help Files)
6. It should say 'Well done account is balanced' and you can click OK
7. If you still think there is a problem then it is with the transactions. The account balances internally now so the problem must be with bad data capture. Print out the statement while it still shows all lines (ie none are archived) and check it manually, marking off each credit to its corresponding debits until you find your problem.
8. Once the account is correct then you can match and archive the transactions again.
Further help on this topic can be found at Finding and correcting bad accounts