Don't worry, you aren't the only one having problem with the MW3 right now, but if you have error code "ce-107857-8" then you're probably having a particularly hard time.
It's the end of the day, you've come home from work or school, and you boot up Modern Warfare 3. Or, at least, you try to.
We know why you're here, it sucks, but there is a solution to ce-107857-8.
How To Fix Error Code "ce-107857-8" In Modern Warfare 3
We hate to be the bearers of bad news, but there is only one known solution to ce-107857-8: Delete every content pack you have for Call of Duty and redownload the ones you want to play. So delete everything, including all the MW2 and Warzone files, and then download the packs you want depending on whether you want to just hop into MW3 multiplayer, or play campaign and zombies as well.
The only reason we think you have to use such an extreme solution is because this error code seems to be a result of the entire CoD HQ app being corrupted. That's just a guess on our part, but it would explain why the error code stops you doing anything.
And there you have it, a short guide on what causes error code ce-107857-8 and how you can fix it. Now get back out there and enjoy the grind (and if you don't know what weapon to use, here is our tier-ranking of every weapon in Modern Warfare 3).