I'd taken the "%1" off of the end of that command, which I'd found while looking for something else in the registry, and since that means that the command would have received a file or path from Opus, I assume that's why it crashes in DOS. I also assume that since I've not been seeing this crash in normal operation, it's probably my fault it's appearing.
I should probably say that I wasn't trying to do anything with it, I was looking for something DOpus related in the registry and thought that might have been related. I dropped the %1 because I know that's DOpus syntax and therefore assumed it wouldn't work in DOS. Anyway, good to know it's already history.