Tagging the file you sent me works fine at my end and so, especially since you're seeing the same thing in other programs, I suspect the issue is being triggered by something you've got installed.
Both Explorer and Opus (I don't know about other tools) allow shell extensions to modify how metadata is stored in files, so checking which relevant shell extensions you have installed makes sense.
Download the latest version of ShellExView and run it. Choose Options -> Filter By Extension Type and then select just MetaData and Property Handler. If there is a problematic component, it'll probably be shown on a red background (non-Microsoft components are shown that way). Try right-clicking it and disabling it to see if that helps.
Here are the extensions I have, so you know you can probably discount these ones and focus on any different ones:
It could also be something like a tool that is locking the file you are trying to modify, though probably not given the way it fails with a half-written temp-file.
Also, make sure you're using the latest Opus code (10.0.1.1 at the moment, link in my sig) so we're both testing with the same thing.