Hey I made some progress... is everyone using the same sound card for system audio and also daw use? I noticed my RME driver not changing with a buffer change while recording vocals the other day... tracked it down to the system audio (windows 7). As soon as I disabled the use of my RME in windows, cubase was switching the buffer perfectly.
Just curious to see if anyone has the problem even if their operating system isn't using the interface for system sound.