I've been hit with the slow-down bug recently as well. Apparently, this's been an issue for many PD10 users lately. As to the root cause, I'm really not sure. Maybe it's the 10.10.1 update (it was running fine for a while after moving to Yosemite.)
Anyway, I've gone back to PD8 for now (running w/o hiccups.) I might ask for a refund if this issue isn't fixed soon.
Anyway, I've gone back to PD8 for now (running w/o hiccups.) I might ask for a refund if this issue isn't fixed soon.