Please re-download the update from our downloads page and see if installing & rebooting again fixes it. (Just install over the top of what you have. Don't uninstall as it would wipe your config and should not be needed.)
Checking the integrity of the installer is also worth doing, in case it is not downloading fully.
Another possibility is anti-virus scanners, some of which are known to freak out when they see a new version of an EXE that isn't yet popular enough for them to have it in their databases. Temporarily disabling the a/v scanner may be worth a quick try.
Rebooting into safe mode is worth a try if that doesn't work.
Crash, exit or high CPU usage when viewing certain directories has suggestions in case the problem is a file within the directory that Opus is showing when it first starts.
Here's the Opus 11.10 x64 installer in case you want to try reverting to that version.