[gprimr1]

I have this problem too, I've been trying to figure out what is causing it.

I have noticed that it occurs both at high and low signal levels, and while roaming and while on Sprint's network.

I think that it's related to the radios ability to switch between data and voice.

I noticed when I changed by Activesync from "as Items arrive" to "every 15 minutes", it occurred much less often so that makes me think the program isn't sending the right instructions to the radio.

Soft resetting in this cause would then term all open data connections, thus allowing you to send.

I also think it's somehow related to the fact that if the phone goes from sprint to roaming and back, it will get a failed to authenticate when dialing #777 error.

God I wish someone would produce a custom rom for this phone.