missing achievments Gears of War

I believe that file would be associated with your saved games. If those were deleted, then I'm afraid whatever info might have been associated with them will be gone, too. It sounds like you will have to re-discover the tags while connected to LIVE to earn the achievement.

I'm not sure I understand how you got all of the tags in co-op? If a friend had most of the tags and finished the achievement, I don't know that it would necessarily carry over to your profile.

i seem to remember playing halo 3 with a friend a while ago...we were both going for all the skulls in the game. what we did was have one person pick them up and then drop it and have the other person pick it up that way we both got the achievement. however i've never seen cog tags able to be let go in game...so i can understand your puzzlement too

Sorry I did not respond sooner (computer issues).  The cog tags no longer appear in game.  To explain the co-op thing better:  the level clear at diffrerent difficulty achievements (e.g. inasne) disappeared also, when I replayed the game something triggered them without actually having to fully finish the level again.  Since when in co-op a cog taq that neither player has is picked up by one it is rewarded to both; so I used this in an attempt to trigger the re-awarding of the achievements

Did you overwrite your save files (or delete them) when you replayed the game?

Did it have to do with  when you profile glitched your achievements because your first 5 achievements deal with completing the game. Just a guess....

Gaining a higher internet speed does not remove your achievements from your profile mate

The only save data presented on the hard drive for Gears of War is checkpoint data (which I deleted but it had no effect); however, logically, there has to be a file somewhere that saves the cog tag progress.  

Also, sorry if my grammar was off; but, the it I was referring to was either the machine or xbox live.  By the internet, I meant that I was unable to access xbox live until I got it (unavailable in my area until April 2011), and that all of my  previous gameplay had been offline.  

Additionally, some other games' achievements had disappeared, but as of yet I have had no issues with regaining them; in fact one game actually gave an achievement that had not been awarded when it was originally earned.

The cog tag issue appears to be something else, maybe in the way it is saved.  I don't know if it is true, but I have read elsewhere that some games' collectibles get saved, some way, to the gamertag rather than to the game save data, so that one does not have to re-collect them when replaying a game.

In that case you could try deleting and recovering your profile. When deleting, you'll also have the option to delete all profile content as well. While I don't recommend this (unless you take the time to back up your files), it's possible that it could restore the COG tags, if what you read was correct.

The same happend to me, exactly, I did all of the campaign achievements OFFLINE, when I connected to the internet and on to XBL all but three achievements were reset except the COG tags ingame, which I had 27/30 at the time and got the For The Fallen achievement but not the other two.

I'm guessing the save data is like leaderboard data, it doesn't save on your Xbox but it saves on a diffrent profile or something, its just frustrating that Microsoft or Epic won't do anything, yeah its an old game, but some older games like Quake 4 reset leaderboards because of one person boost blocking the number one spot, just a simple reset or possibly a automatic unlock like they did with the War Supportor Medal in GOW3.

I just want this game to be 100% completed for me.