When we try to adjust an unpaid invoice, we are getting the message that there is 'no data to report'.. and when we try to look up the sales journal entry number, it says there is no such entry.  HOWEVER, the entries show up in the sales ledger, and accounts receiveable ledger.  When I go to post a cheque, the invoice number does not show up in the customer's account.

What is up with that?  Is anyone else having this problem or know how to fix it?

This usually means it has been reversed already.  Look for the original you are trying to adjust then note the Journal Entry number.  Then look down the list to find any entry that says Reversing J###, correction is J###.  This will show you that it has been reversed or adjusted.  If the second J### is the same as that actual journal entry, then it will be a reversal, but if it references the next journal number then it was an adjustment and you need to keep looking.