I have wm6.1 with the 5060 release, and I've had the same problem with a half dozen different distributions. I have wireless sync on my phone, but after wireless sync finishes it's sync session, it hangs up the data connection. Then, it does not reinitiate the data connection next time it goes to sync, so the server it's trying to connect to does not resolve. I tried always on data in the registry, it didn't do it. If I manually open a data connection, it will work, then hang it up, and won't work again.

The strange part is, it worked for a few days, then suddenly stopped. I reflash, it works for a few days, then stops. As far as I can tell, nothing is changing, it just suddenly decides it's time to hang up the data connection.