OK, Twilight Zone time!
After you did your SQL update, if you do a SQL Select statement select itemnmbr,itemdesc from IV00101 do you see the changes? In GP are you going to Cards->Inventory Items to see the descriptions? Are you in the correct company? Make sure when you are in GP that you are not sitting on that item. The update statement would look like this: update iv00101 set itemdesc='New Description' where itemnmbr='Item Number'