once u put the device in gsm only mode before u can get a data connection after changing back the cdma or global(using cdma) u have to retype the username and password of ur device in the connectiion setting!!
Username:
yournumber@vzw3g.com
Password:
vzw
after this is inputed in u have to manually connect to the data!!
found
here
for some reason after going to gsm then back to cdma ur connection setting for cdma are lost!! i am looking for a way or a fix so that try will 1. stay after switching back or 2. a program that will auto pull the info and apply the fix!!