Recently we have detected some stricter rules how Apple enforces installing one of the supported carrier profiles / preference bundles. This also means.. even if you are jailbroken it is very likely that iTunes will install one of these preferences / carrier bundles during a backup/restore or during sync.Then consequently if your carrier opted for it: Tethering may be blocked (including the new hotspot feature in iOS 4.3.1).With this post I want to gather my thoughts and web knowledge how to bypass these restrictions (given you're jailbroken you should have full control over your device).

First Idea:

Install TetherMe via Cydia. http://www.iphonedownloadblog.com/2010/08/15/tetherme-brings-native-tethering-to-the-iphone/

Second Idea:

Install CommCenter Patches for your iPhone and iOS version and then install a custom Carrier Bundle which allows tethering.

Third Idea:

follow this guide:http://forums.macrumors.com/showthread.php?t=1131582and revert to the Unknown Carrier Profile which has no restrictions.