If it was that on its own, I'd suspect a shell extension:
But that, and the other crash, suggests the underlying problem may be something low-level, like a driver or an antivirus scanner. As antivirus would potentially scan a .zip file when it was accessed to build the right-click menu, that makes it a possibility.
If it happens again, you should be able to create a dump file which we can use to see which components are involved in the problem:
While it's happening, please go to Task Manager, then the Details tab, right-click dopus.exe and select Create Dump File.
Do that 4 or 5 times, and it should create something like:
C:\Users\<username>\AppData\Local\Temp\dopus.DMP
C:\Users\<username>\AppData\Local\Temp\dopus (2).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (3).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (4).DMP
C:\Users\<username>\AppData\Local\Temp\dopus (5).DMP
The files will be large, but compress well.
If sending more than one file, using the 7z format instead of zip will give a much reduced size. You can do this via the Archive Files button in Opus.
Please zip or 7z the files and email them to crashdumps@gpsoft.com.au (it's best not to post full dumps publicly to the forum).