since your stats and weapons and classes are stored online..do you have steam cloud enabled in your options.
I dont know if its super important but it is a feature to ensure your stats are kept available for you
I'm not saying that you are doing this but a lot of people tend to just hit Escape when the "Downloading Game Settings" screen pops up to get it out of the way, as sometimes it can stay there for a while. The statement is actually quite misleading cause when that screen pops up it is actually uploading your changes to their master server.
This can cause you to lose recent class/killstreak/playercard changes as you are essentially interrupting your info from updating by pressing escape.
Perhaps the statement should read "Saving your Settings - Do not press Esc" or something along those lines.