I was having the same problem using Dial-dictate 4.0.6 .... We recently upgraded to the 4.0.9 and the random disconnects seem to have significantly diminshed, if not completely disappeared.
A few other things to try for the D/4PCI ( I have the same card):
In Dial-Dictate:
- Disable Software Based end of call.
- Set the end of call detect delay as low as possible... this may add dead air but wont cut the call (mine is set to 500).
- Reduce the DTMF tone detect delay - may add tones to recordings if its too short (mine is at 150).
In DCOM configuration manager (you must stop dial-dictate before configuring the modem):
- Select the D/4PCI under: Configured devices=>D/x1D-PCI=>D/4PCI in slot xx.
- Double-click to open the properties.
- Select the Misc. tab and set "Disconnect tone" to No
This seems to have resolved the issues for us. Not sure if it will, or will not, do the same for you but it may be worth a shot.