After some investigation it appears that the "optional HDD install" is the culprit. SEGA advises those who are suffering lost saves to uninstall it from the HDD and play from the disc.
Xbox 360 would seem to be the only troublemaker. The critically marred Aliens: Colonial Marines has debuted atop the UK chart, chest-bursting ahead of Dead Space 3.
"We've received reports that a small number of users may be experiencing problems with saving their progress after completing the game's optional HDD install," acknowledged SEGA.
"If you experience any issues with your save game data, please try uninstalling the game from your HDD and playing from disc while we investigate what may be causing this issue."
Aliens: Colonial Marines released on Xbox 360, PS3 and PC last week after a turbulent development.