I was getting this error every so often -- my Up/Down arrows for 3G would just "stall" -- totally grayed out. Then like you, I would toggle Airplane mode .. and recover 99% of the time. I installed the "Speed test" APP from market that I run when I see this problem ... just in an attempt to isolate the problem -- whether it it a local Server or what.. It seems, from what has been posted, that this "loss of 3G" thing is being addressed in the pending fixes. Good luck.
Check you settings for the Battery Profile... You may have the timeout set wrong for your common use habits. I had to use the Cutom option to get mine to work without issue.
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Try enabling your data roaming on the device. Follow the link below to enable the data roaming.
http://support.vzw.com/clc/devices/knowledge_base.html?id=33954
I have just came across a app that help when data connections seems to go dormant and a restart is the solution,
Download Restart Connection from http://www.appbrain.com/app/restart-connections/com.dazbradbury.restartConnections , it restores connection easily without reboot, just place icon on desktop and trigger to reboor connections.