A little late on this reply. I'm assuming you mean that Assets do not equal Liabilities + Equity on the balance sheet under Cash Basis. I have encountered this problem before, and each time it was caused by a corrupted data entry.
To locate it, first determine the year when it started (run the balance sheet for previous years and see in what year the balance sheet goes out of balance). Then, to narrow it down, run the balance sheet for the first six months, and then the last six months, to see which half of the year the bad entry sits. Do this iteratively until you locate the day.
Then, try to look at all transactions on that day that affect the balance sheet. Run the balance sheet for the date you've identified and then double click on each account to look at the transactions in that account. Often the "bad" one will pop out, as it usually is the amount of the imbalance, and usually in A/R or A/P. When you locate it, record or print out the transaction so that you can put it in later. Delete the transaction, and then enter it again. You can then confirm that the problem is gone by re-running the balance sheet, and all should be in balance.