I am suddenly getting the same error

I'm not certain what is causing that, and I won't have a testing environment for a little bit.

However, people have said that changing the directory where it's run and disabling installed mods detection works as a temporary workaround.

The issue was on BeatMods' side, should be fixed now.

Yeah no, its not fixed I am bloody trying to get the mod assistant to work but every time its sending that same bloody error saying either the IPA.exe is in use or the bloody songe-converter.exe is in use, AND THATS JUST TRYING TO INSTALL THE 2 DEFAULT MODS! Bloody fix this already.

Oh my word this program is so stupid, it keeps on saying another process is using the program, WHEN IT IS THE OTHER PROCESS THAT IS USING THE PROGRAM, HOW STUPID CAN IT GET

That sounds like a completely different issue. Try disabling your AV and seeing if that works.

It didnt work