I have the same issue with sales orders showing in the "Open Sales Orders by Customer" report with an Amount but no Open Balance.  More so, the sales order does not show up in the "Open Sales Orders by Item" report.  Running the Verify and Rebuild Data did not solve the problem.  Here are the actions that I took to resolve the issue:

1st Action - ran Verify utility and then Rebuild Data utility.  Did not solve the problem.

2nd Action - on the sales order I deleted lines that did not show as closed (such as a blank line and there was an open line with just some text as a note) and Saved & Closed the order.  This did not solve the problem.

3rd Action - on the sales order I entered some text into the MEMO field and Saved & Closed the order.  This worked!