does anyone else have problems with the game not automatically saving the game?

sometimes the game play through fine, saving afer major objectives have been completed, or i've survived a a big gun battle..... then sometimes... it wont save AT ALL.... i've played thru almost 20mins before now, without it saving... something that isn't exactly easy to do... its VERY frustrating when it happens.... because you just have to hope you complete the section....

anyway, just wondering if anyone else had or heard about this problem....