Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.

Actually, it's an easy fix.
You need to edit a section in the aircraft.cfg file. Look for the [GPWS] section and edit the parameters.
Here is the one I use to disable the callouts:
[GPWS]
max_warning_height=-1
sink_rate_fpm=-999999
excessive_sink_rate_fpm=-999999
climbout_sink_rate_fpm=-999999
flap_and_gear_sink_rate_fpm=-999999
It should because you end up disabling the callout on the sink rate.But will this mod fix the "Don't Sink" problem?