This is a classic reason why the class action mechanism exists - relatively minor individual damages all things considered (either the price for the download or the price for the original content that is wasted because of the download) but massive when the loss of each individual class member is accumulated, common questions of law or fact relating to each individual class member, and the claims of the would-be named plaintiff are typical of the unnamed class members.  Rule 23, Federal Rules of Civil Procedure (and most state rule 23s).  I'm sure the company that is not willing to provide its customers with an immediate refund or any type of real solution, has a list on a computer somewhere of all of those who actually purchased the download, or it is relatively easy to get through judicial procedure.  Then it's a matter of having an expert testify as to the reality that this download ruins 90 percent of the existing gaming experience (having nothing to do with an individual user's connection), have another expert testify as to the calculation of loss for each individual member, then multiply it by every person who bought the product, without having to have 100s of 1000s of people testify.  If an immediate patch is not provided for download, or an immediate solution other than the nonsense above of connection issues, I will continue to look down the path mentioned above.

I have this issue also. After the purchase and install of DLC4 I am no longer able to find games. I am in the United States,, and am very frustrated by this.

I want a refund of DLC4..

exact same thing for me.  after installing dlc4, it would take a long time connecting to MW3 servers (xbox live is fine), sometimes timing out.  Eventually I connect, no capture the flag games, no kill confirmed games, eventually a domination or deathmatch game, usually only 1 or 2 potential games.  The games I do find are usually with the same people - day after day.    UPDATE - After downloaded another mappack, I'm finding games again.  Maybe the combination of mappacks is causing the problem???

Update: Tried again this afternoon. Same problem - no matches to be found anywhere.

BUT! I disabled DLC and only played the original maps ('back' button on the controler when connected to Xbox Live in multiplayer) and suddenly everything worked fine. Every game mode, 45-50 matches found.

The only DLC I have so far is 1 and 4, and all of this started after buying DLC4. Very annoyed.

Been having this same problem all day.  To think that 3 months after the fact this issue still hasn't been addressed shows a blatant disregard in serving your customers.  Shame on you Activision.  This may very well be my last COD and my last reason to buy LIVE again.  If they could care less about fixing this product then they can choke on whatever COD they try to sell me in the future because I won't buy it.  Not after this cluster F!