I use older Replay Gain Scanner component for consistency with the rest of my collection. Newer Foobar warns about it and exit. There should be a way to circunvect or disable that checking, maybe with a switch on launch under userrs responsability. It's annoying to have to use newer plugins if desired behaviour isn't user wish...
What version of Foobar2000 are you using?
The latest beta version has an option to switch it back to the classic replaygain so the plugin shouldn't be needed.