I've ran across something multiple times and thought I'd mention it.
Tune the 990 to any old FM station. Press the direct button on the remote, type in the station you want to go to, press Set and all is good. It goes to your station, and no problems. Now, if you press the direct button, type in your station, and press Enter, it fails to go to your station, and for me the 990's tuner is locked up. If I press PScan, it does nothing. If I press AM/FM toggle, it does nothing. I end up having to turn the 990 off and back on.
Anyone else experience this? If I'm not an isolated instance, I can let Outlaw know. It is not a big deal. Doesn't bother me really since I know the right way to do it, but figure they ought to know.

I don't remember running into this, but I don't think I've tried hitting ENTER during the direct access process (I've always gone straight to SET).

I think I know why I've never done this - it's because I'm using an MX-700 rather than the original remote. The only ENTER label I'm seeing on the original remote is a secondary label for the button whose primary label is MENU. Since I have that button mapped to MENU on my MX-700, I never think of it as an option. What's happening when you press ENTER during direct access is the 990 tries to go into the menu while the tuner has no station specified, so I wouldn't be surprised if that caused it to get confused and hang up. If it does affect other units (which seems possible, although I haven't tried it on mine yet), it would probably be an easy fix to cancel the direct access command and revert to the previous station when unrelated commands (such as MENU, an input command, a surround mode command, or other signals) are received.

Yep, I agree.
Also, I did run into it with the original remote. I also ran into it with my Harmony 880 because I was doing some key-mapping and just happened to choose the "Enter" command to map to a given button rather than the "Select" command. The "Enter" command is the incorrect one and locked the tuner. But since I had previous experienced this with the original remote, I knew what I had to do to fix the issue.