I did a factory restore, and in the process I upgraded from Gingerbread to Ice Cream Sandwich - although I am not sure I did it correctly.
When I look at the "About Phone" section, the Android Version says: 4.0.3
The Baseband Version says: 19100XXLPQ
Build Number: IML74K.XXLPQ
(Cant remember where it used to say Gingerbread lol, but it doesnt say Ice Cream Sandwich anywhere)...
Anyway, since I did this, I can no longer hear people during a call.
They can hear me, but I cant hear them.