[lnando84]

found this in a hd2 thread and it might work.. someone wanna give it a try and let us know if it works..

For those who find that an incoming call goes too quickly to voicemail and does not give you enough time to answer it you can increase the delay up to 30 seconds now. Go to Settings, Personal Tab, Phone, Services, Call Forwarding and Get Settings. You can change the delay from 5 to 30 seconds under the forwarding option. If that does not work based on your carrier, try this:
reg edit: HKEY_CURRENT_USER\ControlPanel\PhoneCallFwd
change "DelaySeconds" value to 30 which should indicate 30 seconds.