Dell XPS 8900: No keyboard during Windows Setup

We have a Dell XPS 8900 that has no response on the keyboard when in Windows setup.  Mouse works OK, but on some setup screens not at all.  The problem is that we're trying to get into BIOS setup, but it won't let us because it doesn't seem to register keystrokes.   The keyboard and mouse are a wireless combo with a USB receiver.  Are there settings in the BIOS that need to be updated to allow this to have better compatibility?  They worked fine up to a few days ago when Windows was working.