After following the instructions by the dev team for enabling tethering in 3.1.2, and downloading the Benm mobile config as per instructions I ran into what turned out to be a common problem. With the Benm config file, I lost VVM, without the config, the tethering option on my 3GS would disappear as soon as it was plugged into my computer. It seemed as though many of us were left with a choice, either we get tethering, OR visual voicemail, but not both. I then did a little research, and came across this: http://appadvice.com/appnn/2009/10/31-tethering-visual-voicemail-fixing-the-benm-mobileconfig-file/. After removing the Benm profile, and downloading the one on this website, and doing a network settings reset, I got both VVM and tethering! It seems as though there is finally a solution to those with this problems. This was posted while tethered to my 3GS, and receiving 2 new visual voicemail notifications in the meantime! If posting the link violates any rules, please let me know, and I will delete it.