I have exactly the same issue. I use QuickBooks since 7 years. Now I need to issue a new invoice with new products but I can't add new products because they have slash character " / " in the name. Even when I try to edit existing product which has slash / in it, Quickbooks won't let me save it.  I can't work without /.  What happened?????

I just read that there is a list of acceptable characters where Quickbooks uses / in the list but the slash is not on the list of acceptable characters but there are some characters which probably nobody will ever use.

Bring back slash sign /  !!!!!!!!!