>Sorry, but I don't see how that index is reletaded to the problem you have.

I don't know either. But, in order to resolve the issue, I had to do this:

      SELECT * FROM Temp WHERE OrderMain>0 INTO CURSOR TempForum
      SELECT NoClient,MAX(OrderMain) AS SortOrder FROM TempForum GROUP BY NoClient ORDER BY SortOrder INTO CURSOR Temp2

So, basically, I had to select all records having a value in OrderMain into a cursor. Then, from that cursor, your command is working.

Thanks