As far as I know that should work. For some reason it isn't picking up the double && on the one entry. I would try putting three & in there and see what happens.
I would also try copying the code into a text file, deleting it out of access and recreating it. I have not seen this on code, but I have seen cases where access's internal representation and the typed string got out of sync on queries.
One work around you can try is using chr(38) to add it directly.