Its unlikely this is a firewall issue because you are able to get the files downloaded, which would not occur if CC was blocked at the firewall. "Access Denied" tends to point to a local permissions issue.
Because of this it becomes less likely an uninstall will sort the problems, unless by coincidence it is able to delete the folder or file that is causing the problem but if the app has a permissions problem, that may not happen either.
Bear in mind that 'admin' access doesn't necessarily let you access everything in Windows (7,8.x or 10). You may have to explicitly seize permissions to give yourself the rights needed.
Unless there is an event log entry which tells you explicitly which folder is causing the problem you've got some hunting to do.
As several have mentioned above, I'd suggest uninstalling Command Center. However before proceeding to any other steps I'd also go through the file system and look for anything that was not removed. You may stumble across the errant folder or file causing the problem. If you cannot delete, sieze permissions (right click, select security, then check the permissions on it to make sure you are the owner). Then delete that fecker with extreme prejudice.
One thing I've not seen above (apologies if I missed it anyone) is to reboot your system into Safe Mode and then attempt uninstalling. It is possible a file is flagged as in-use, correctly or otherwise, and that it is preventing the process from completing successfully. I tend to lean towards it being a permissions issue but this is an option worth testing.