Today, I wanted to use some of my carrier USSD codes (e.g. *120#) on my Galaxy S and they didn’t worked.
I entered them, but the Galaxy refused to display anything. After some searching I found out that this comes from the Mobile Tracker I had activated.
As soon as you active Mobile Tracker (Settings –> Location and security –> Mobile tracker) no USSD codes will work.
Disabled Mobile Tracker and the codes were working again. Go figure…