Why am i not able to save any more levels for quake 4 on xbox360?

This is with quake4 as played on xbox360.I was able to save up till aqueducts annex in quake 4 but beyond that how many ever objectives i complete it is not getting saved. So i have to start all over again from aquedects annex. I still have 107 GB of free space on my hard drive. Can anybody help me?