Shared Internet on MacBook no longer accessible to iPhone

My iPhone 5 had been successfully accessing the wired Internet connexion on my MacBook Pro (running Snow Leopard) shared via AirPort, until recently the iPhone just refused connecting again. Any other WiFi device, for example my router at ome, can be accessed fine. The configuration for the Internet sharing on my MacBook that had worked fine previously was as follows:

• channel = Automatic
• 128-bit WEP activated
• password with 13 ASCII characters

Note that the iPhone does see the available network thus generated, but merely spins endlessly in an attempt to connect to it. Trying to force a reset of this network in the preferences of the iPhone through the setting "Ignore this network" does cause the password dialog to reappear, but keing-in the password again makes no difference: the network remains unaccessible.

I've also tried resetting the network settings on the iPhone through the General preferences / Reset panel, but to no avail.

Any suggestions, hopefully other than a complete wipe out of the device to factory settings which would force to subsequently reinstall everything from backup?

Many thanks!