Check the basics three times:
1) Codecs
2) Static routes outgoing from the quintum
3) Dial peer pots coming into the Cisco.
4)Prefix on the route.
Enable the call log on the A800.
Do ev +ch
Clear the log ( ev c)
Make a call Pull the log ( ev )
Post the result or email to mike3799@yahoo. I will take a look.
Best luck!!!!!