I recently noticed something mysterious about my N73. Whenever there was an active voice call, whether incoming or outgoing, a data connection was established at the same time. Hang up the voice call, the data connection also went away. A natural initial diagnosis was that some virus or Trojan horse or spyware or malware was trying to phone home. But Connection Manager showed that the connection was completely idle without any data traffic at all.
Tasky shows that whenever a voice call is made, a new sipprofilesrv.exe is also created. So it seems to be related to SIP. Indeed, I have a unregistered SIP profile with a valid access point under my SIP settings. Deleting the profile solves the problem.