Ti 89 Titanium
The only option or keys that will work is the ENTER key and the arrow keys. Try to get your arrow key to work by arrowing down and hit enter hopefully change you to something different.
Next, if at all possible can you hit the MODE key or get into the mode. If you get into the MODE select F3 and then arrow down twice or all the way to the bottom and at APPS Desktop select 1:OFF and then hit the ENTER key. Next, What I really think you need to do is reinstall the Ti 89 OS software. To do so you would need to connect to your computer or another Ti 89 Titanium to your Ti 89 Titanium. If you have Ti connect computer software (from the Ti site) connected to your Ti 89 Titanium it might help you more in troubleshooting any further problems too. You might be able to delete corrupt files that would free your calculator up and start running better.