Recently purchased the Apogee Symphony IO so I could stop working with Digital Performer in DAE mode. Initially I was having terrible trouble getting usable functionality using DP in MAS with the Apogee. Then, based on a tip from Motunation.com, I went into DP Prefs, went to the plug-in pane, and selected "Virtual instruments in Real Time." Voilà - problems gone. VE Pro does not like "pre-gen" mode, at least as implemented by DP.
Just hoping to save others from days of hair-pulling!
Peter