Call VM, request that they reset your sockets, after 5 days with speaking to Tech Support on this issue, they strolled through a plethora of "fixs" i.e.: Refreshes, Hard Resets, Manual Programing, Network Resets, & finally the Socket Reset. The last of which got me back up and running.
Their also seems to be an issue with CM7. I do not know what it is exactly and i have not done any troubleshooting with the MOD (do to the fact that my MT is my primary phone and i need it functioning) restoring to STOCK would allow me to receive messages and all was fine for hours, until i decided to re-flash CM7 which would work for small intervals at a time but then fail. I then upgraded to CM9 and have no other issues. (with the exception of a few send errors) Hope this helps your solve your debacle