I also faced the same problem with my 9550, i can't scan my laptop ad-hoc signal, i tried many times even after reset and re-create the new network.
When i tried with nokia e72 belong to my wife, it working very well, it's can detect the signal very strong. I can access any websites via e72 phone which connected to wifi of the laptop whether at kitchen or bathroom,
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From my investigations, i found that the nokia e72 can be used in both ways, 1) through internet plan (directly via the phone which has internet data service) and 2) without internet data plan (connect via wifi of the laptop adhoc signal). Its can do in flip-flop at once time. You can close internet plan and use wifi of the laptop, or vice-versa. I did many times using e72.
For BB, its seems many of them (or maybe all of them) cannot do like what e72 can do, like hrbuckley said, BB cannot connect to wifi from adhoc signal of other device like laptop, it only can be connect to the infrastructure network, SO SAD. We only can access internet after having the data plan from the wireless provider.
So, my conclusion is BB only has one way to access the internet, through internet data plan from the wireless provider, not from the adhoc network.
Correct me if wrong.