I'm really hoping somebody can help me here as I'm getting ready to sell my 360 and not bother with a new one.
The problem started when I was playing Transformers: War for Cybetron - I got to the last mission and completed it, as you would, when I noticed that the achievement that popped up on screen... hadn't saved. So I repeated the mission and the achievement popped up again so I went into the 360 guide (middle button) and saw that 1. my gamer picture had been replaced by a Grey, gradient square and the blade to the left showed that I had 0G, even when expanding the achievements menu it remained at zero.
It was later on that I had the random idea to remove the empty memory card from the front of the box and repeat the mission one last time... which thankfully worked and the achievement and game progress were saved.
Now... I recently bought Dead Island and Space Marines and haven't used my memory card, or even plugged it in again, since that time but it seems to be happening again.
Exactly the same thing is happening as before only with different, multiple, games so I know it's not an issue with the disc or anything.
What happens, especially with D.I., is; I will get to a certain point (main checkpoint) and it will attempt to save and is successful... until I get an achievement - whenever I get one; it just comes up with the message, in D.I. style, "Save Error - Could not save progress due to the storage device the Gamer Profile is saved on is currently unavailable" or something to that tune.
I've missed out on quite a few achievements as they didn't save first time and won't trigger again unless I start a new game... and I keep having to repeat certain missions as most of the time they don't save.
If it's any help to you guys; I'm on a 360 Elite and I install most of my games to the HDD until completion, I've deleted around 20GB of data thinking it was a space issue, found some "incomplete" files for a few games and deleted them and nothing has worked.
Like I said; I'm ready to sell up and not bother so help would be greatly appreciated - even more so from you official XBOX guys