Hi,
Matt and Tristan have given you the same advice I would. I see you are on GP2010 so you do have the reconcile tool in GL. The Excel spreadsheet that routine creates might appear hard to understand, but it will expose to you where the differences are. If it were me, I'd go back to the last date everything balanced and set that as my 'From' date. I'd set the current date as my 'To' date. Run the utility. On the spreadsheet produced by the utility, I'd initially ignore the 'matched' transactions and concentrate on the Unmatched and Potentially matched transactions.
Let us know how it works out.
Kind regards,
Leslie