Try opening the VBA editor (by typing Ctrl-G) and selecting Tools...
References. If any are marked MISSING, write down the name of the
reference, uncheck it, close and open Access, and check it again (you
may need to scroll down to find it); close and open Access again and
see if that helps. It might be a library which existed on the computer
with A2003 which does not exist on this computer; in that case you'll
need to install it, or remove it from your code.