This worked for me anyway .... no guarantees but it could help you maybe...
I had issues since upgrading to iOS4 on my 32Gb 3GS connecting to WiFi hot-spots...
I'd read various posts about it being a possible WPA2 incompatibility etc..
What i've done here at home (this was 1st chance i had to do it) was install a setup profile using the free iPhone Configuration Utility
This way you can setup the hotspot, the password for any encryption (i'm using WPA2 exclusively on my Airport Extreme) etc for your own home, and any common ones (like in UK you could setup the BT Openzone one too) you know about.
It just might help
I had issues since upgrading to iOS4 on my 32Gb 3GS connecting to WiFi hot-spots...
I'd read various posts about it being a possible WPA2 incompatibility etc..
What i've done here at home (this was 1st chance i had to do it) was install a setup profile using the free iPhone Configuration Utility
This way you can setup the hotspot, the password for any encryption (i'm using WPA2 exclusively on my Airport Extreme) etc for your own home, and any common ones (like in UK you could setup the BT Openzone one too) you know about.
It just might help