I think this is it:
Wifi and Phone @ same time
Go to key: HKLM/Services/WirelessMgr
Find a key called 'MutexFlag'
Change it's value from '1' to '0'
This was on
http://www.cmz727.com/alan/6700/6700.htm
near the bottom of the page.
Others on
http://wiki.xda-developers.com/index...ame=HTC_Apache