welcome to the loss of flexibility that sometimes accompanies body building. However, this does not have to be the case. With proper stretching on a regular basis, you do not have to lose any flexibility. So remember to stretch!
I'm not sure if its the inability to turn around is from loss of flexibility or simply from the extra beef which inhibits our range of motion. I heard a rumour once that Dorian Yates was unable to even touch his face when he was right pumped up.