Yeah that's bad. Normally if you can't get into an app or setting you can go into Manage Applications and clear the data for that app. But... how do you do that for Manage Applications itself?
It's likely some corruption or dodgy data in one of the application titles. You might try uninstalling some apps using the Market that you've installed or updated recently. They're arranged in the order you've updated/installed them (most recent at the top) in the Downloads section of the Market.
