It's best to not run MC as administrator
Matt is right. You really can't do it that way.
If the UAC prompts are annoying when the updates are available, then either:
1. Disable UAC entirely (I don't recommend this, and it breaks Metro on Windows 8 if you do it).
2. Turn off the auto-updater entirely and update manually (maybe set a calendar reminder to come here and check for new builds once a month or something).
I suspect something is borked up from running things as Admin. This is usually a Very Bad Idea on Windows, unless you know what you're doing. It, essentailly, makes that application run as another user, and isolates it from the logged on user's processes.
Reinstall MC19 without doing anything fancy (just double-click on the installer, you also don't need to run it as an admin, it will automatically elevate as needed).
See if that solves your problem.
If not, uninstall MC (
preserve both the registry settings and Library as part of the uninstall), reboot, then reinstall.
I think your copy of MC is "owned" by another user, and is acting funny.