I am having similar difficulties. The plugins do load in PTHD 8.0.3c2/Mac 10.5.8 but are totally erratic in their function. All of them do respond to midi note but mouse control does not work so editing is not possible. Some may respond to midi program change but no other midi messages and quitting Prophet causes PT to crash. I have done a complete reinstall of all Arturia synths including trashing prefs. The stand-alones work intermittently as well. With the plugins and stand alones exhibiting a variety of these wonky behaviors, none of which seem to correspond to any particular procedure, makes it almost impossible to diagnose.
ARP 2600 v2.0
cs80 v2.0
Jupiter 8V v2.0
miniMg v2.01
Mg Modular V v2.5
Prophet V v2.0
I have been trying to reach technical since April 2010 with no response.
Maybe this will reach technical.