Make sure nothing in the config you imported is pointing at network drives which no longer exist (or don't currently exist). There is a 30 second timeout in Windows if something accesses a network drive and the OS gets no response from the server. (We try to only access them on background threads, but there are still situations where they can tie up the UI thread.)
This includes Favorites, and also buttons on toolbars that point to such paths, or have icons that are on them, and anything like that.
The problem may also be caused by something else in your configuration. If you want to check that, the fastest way to get back to a default config is to uninstall Opus, then install it again. (Uninstalling wipes the config.)
Make sure you still have your config backup before doing this, but don't install it until you've checked if the problem still happens.
Shell Extensions which other software has installed can also cause problems like you describe:
Please don't use custom uninstaller tools unless absolutely necessary. They are more likely to cause problems than solve them.