Replicant

After a long period of time, the data connection on my HTC Magic 32B disappears (the '3G' or 'E' icon stops appearing) and any attempt to use the mobile data connection ends in a failure to resolve a server.
Whenever a voice call is placed when this happens, it will be stuck on the Dialling screen without connecting through.
Also whenever the device is placed into Airplane mode in this state, the option will be greyed out but it will never disconnect from the network i.e. bars still show up in the status bar.