In your voip dial-peer, you may need a "progree indication" command line in order for the VG200 and the PSTN to be in synch with the state of the setup of the call.
This is an example of one of my dial-peers:
dial-peer voice 10 voip
preference 1
incoming called-number .
destination-pattern 8...
progress_ind setup enable 3 <------------------------------------ this
voice-class codec 1
voice-class h323 1
session target ipv4:10.146.124.10
dtmf-relay h245-alphanumeric
fax-relay ecm disable
fax rate disable
ip precedence 5
no vad
Mike Shintani
Cap Gemini Ernst & Young