On my htc desire S (Android 2.3.3) I can't seem to be able to create a normal wi-fi hot spot (that is, sharing my mobile internet connection). What happens is that when I enable the hotspot it somehow automatically disables the mobile network connection (the icon disappears from the top right) and the hotspot takes control.
It's same thing when a normal wi-fi connection take precedence over a mobile inet connection, because it's better. But in this case this is exactly what shouldn't happen. So what I am left with is a hotspot without the internet connection. I can connect my laptop to it, but there's no internet access.
After I disable the hotspot, I can't use my mobile internet connection unless I restart it.

Less important (but maybe relevant): While to hotspot is on, I can't use my wi-fi either, but that seems somewhat logical (even though I don't see why you is it absolut necessary for it not to work - it's probably using the same thing for another protocol, but that's a different story).

All right. I got to the bottom of the problem by searching a little on google (which I should have done before posting here). The problem was related to the mobile network settings - which were adapted for Orange - access through their portal, whatever. For anyone interested, you have to go to the Access Point Names (settings - wireless&networks - mobile networks - access points names) and change the settings there. I simply reset it to the default settings (but that not always the case, as I've read).