Make sure you don't have mapped drives, favorites, toolbar buttons or icons, etc. pointing to network drives that are not accessible on the network.
Antivirus can also cause (usually) short freezes when inspecting exe/dll files or reading icons out of them. In some cases those affect the whole process.
If neither of those explains what's happening, you could send us some process snapshots made while Opus is frozen, which may reveal what's happening. They must be made during the freeze; if they're made just before or after it then they probably won't reveal anything.