I wanted to be sure it wasn't 3.5.1 (I synced and built it after reinstalling), so I reinstalled it again (clean folder, using the installer) and tried the mod on 3.5.0, got the same error again...
It's probably a config file issue, but it should be correct if you downloaded the latest version of BetterKeys. Given that it is happening after Interchange make sure that in the config file it says "The Lab": instead of "Labratory":