BTW, this sounds very similar in that even though in my case I am using the MWI-Account parameter, if I leave the phone alone it sometimes will show MWI after several minutes (30?). It also may show up after a VM is left, but always lost after a restart of the phone. In my case though, if the VM matches the phone account then there is no problem, only using MWI-Account which I need. This symptoms make them sound related.