Found this possible fix for error 498:
Setting>Applications>Manage Applications>Google Play>Uninstall Updates
My youtube app's been working fine, you may have gotten an over-the-air update to your operating system that broke something. You can try reinstalling the affected apps.
Some apps are flagged as built-in and can only be updated, or rolled back. Others you can fully uninstall and then reinstall. If possible, uninstall and reinstall the youtube app.
If that's not possible, you might be looking at a factory reset. Typically you lose all your app settings, but it may be able to pull phone numbers and contacts from from websites like gmail, facebook, etc. ...that's what I did when I first switched to android and I got contact info for everyone I ever knew, plus a few dozen I don't lol.
You can do a backup with a special backup app like Titanium, but it requires rooting your phone. That's a whole nother ball of wax and is not difficult but it voids your warranty.