complete backup gives error message about sales orders or estimates have problems

I am running 2009 Quickbooks Contractor edition - About two weeks ago,I started getting an error message when I did a complete backup - saying that I had an error with Sales Order or Estimates has a problem - I have rebuilt the data file and am still getting the same messge when I do a complete backup.

I have checked the QBWinLog and see the two estimates that it shows are having problems - I am showing various errors (Error: Verify Target: Invalid Open Quantity: Target = 783714 Master = 748935 View = 24.) and (Error: Verify Target: Invalid Received/Invoiced Flag: Target = 783714 Master = 748935 View = 24.) with various #"s.

I have opened the estimate and resaved, opened each progressive invoice checked it and resaved and opened each payment checked it and resaved. But I still get the same error when I do a complete backup.

Anybody got any ideas ???

Thanks

Barbara