I had the problem too and figured out how to fix it. Here's the fix for IE:
Have the browser open to this forum.
Right click anywhere along the top blue area. You should see a list - Menu Bar, Favorites Bar, Command Bar, it goes on.
If there's no check by "Command Bar", click on it.
You should then have a bar at top with the option "Tools", click on it.
Go to "Compatibility View" and click on it.
It will add this forum to a list and it should fix the problem of not being able to use the enter key.