I also seem to be experiencing 'dropped calls' on the iphone 4, (week old), UK, with bumper, Zagg 'invisible shield' and in an area where I never had dropped calls with iphone 3g! Not exactly impressed so far!! Signal strength seems fine. Sometimes redialling works, other times have to 're-boot' the phone. Looking pretty shoddy so far from the 'Jobs' lot. Shame really- lovely device, has almost everything one could want from a smart phone....apart from good 'phone' abilities.