There is a solution. However your phone will still crap out and require a restart occasionally.
The solution is inside the XmBlackberry software. You want to look at "gprs_protocol_fix". They describe the problem in detail, and how to fix it in your ppp connect scripts.
Here's the script I use /etc/ppp/peers/curve
pty "/usr/local/sbin/gprs_protocol_fix /dev/rfcomm0"
I use small connect/disconnect scripts, you can change this on your own, as this is dependent on your provider. =)
My curve only seems to work via bluetooth, no matter what it won't see the modem over usb. Also, on T-Mobile it is terribly slow over EDGE.