Oh, no wonder then, you are only supposed to install and use the mono plugins, when using Logic, as your host app. That is what they were specifically designed for. It is in the manual and readme file. Uninstall the plugins and re-install just the regular stereo plugins. There is an option, at install, to select/de-select the mono versions. Make sure this stays de-selected. All audio hosts (other than Logic) will recognize and properly use the UAD-1 stereo plugins, as either mono or stereo, depending on the source material. The Fairchild 670, should be the the only plugin, to still have a mono version, after you re-install the correct versions. The Fairchild does normally come with a separate mono/stereo versions. This does work with other apps, like SONAR, BTW.
Cheers,
Billy Buck