Hi, first post, I am new here, been downloading all the cool stuff for my Treo 700wx
The problem is you only have one radio built into the Treo, and it is either in Data or Voice mode. Like you can't be on your phone and on dial up internet at the same time; the line is taken up by one or the other.
If you set your Activesync to only sync manually and go up to the "EV" icon next to the signal meter, click on the EV icon, then select disconnect, you should be able to avoid missing calls in 1X areas.....problem is then that you only have on demand data, and you won't get email as it arrives.......