Enter / Return key stops working

This happens after days, right? Try killing the running programs one by one. It's possible that one piece of software has a memory leak and gets increasingly bloated over days until it starts doing weird stuff. Use the Task Manager to be sure their are no applications running, then check whether Enter is still locked out.

The other thing that occurs to me is a keyboard shortcut being assigned to Enter. I don't know that this could happen spontaneously, though.

Finally, in most programs Ctrl+M substituted for Enter, but many Windows programs now don't allow this.

This is a known problem with Phrase Express. Had to hard kill it too since quit wasn't shutting it down.

Apparently you can stop it from registering enter in expert options as described in this Stack Overflow answer

In PhraseExpress, please disable the expert option "Route TAB and ENTER through PhraseExpress" if you experience problems those keys.

Screenshot:

Please also note that using multipe Text Expander simultaneously may introduce interferences as you experienced. Unfortunately, there is no way to get around this limitation for us vendors.

Michael Schmidt PhraseExpress Team