Why doesn't my SIM card does allow a connection to this network? In Android 2.2 from a HTC Desire Z I am frequently finding my phone disconnected from my mobile provider.

When I select my provider from the Settings -> Wireless &amp; networks -> Mobile networks -> Network operators -> Search networks -> &lt;My Provider&gt; I get the message "Your SIM card does not allow a connection to this network".

The only fix I can find is to restart my phone. Problem appears to widely affect Android phones.
It appears several sites suggest preventing the phone from using 3G. I have gone into Settings -> Wireless &amp; network -> Mobile networks -> Network Mode -> GSM only.

This appears to have fixed the issue for me. Of course this wouldn't be a solution for anybody who relies on mobile data (but my provider charges so much for data that I'm wi-fi only).