I have a new Latitude E6430 and have the same issue.
No matter which keyboard layout I use, I cannot get teh Euro symbol to on the 5/% key to work.
I also have an older Dell Latitude D620 with the Euro symbol on the 5/% key.
Neither keytboard has a Alt-Gr key and the right Alt key does not function as Alt-Gr.
Did you find a solution which solves the problem?
