Rename error when entering Sales Order Quantity

I have found that in certain situations, in the standard Cronus database, the error "Do you want to rename the record" is given when a quantity is entered on a Sales Order. I have included a screenshot. At first I could not work out what caused this error, and its occurance seemed random. However, I eventually discovered how to reproduce it:

- Create a first line in an order
- Copy an item number from a separate window, for example from a word doc.
- Paste the item number directly into a second order line, then tab to qty and enter a number.

This is using NAV 2009 R2 unmodified cronus. It seems the important part is to click away from the RTC page, then create a new line without clicking on any other part of the page.

I managed to trace the source of the error to the a CurrPage.UPDATE(TRUE) code on page 46:

QuantityOnAfterValidate()

...

IF (Type = Type::Item) AND
   (Quantity <> xRec.Quantity) AND
   NOT UpdateIsDone
THEN
  CurrPage.UPDATE(TRUE);

Does anyone have any idea what the cause is and how to get round this issue? Maybe I should log a call with MS, but I wondered if anyone else had experienced this issue and found a fix.