It may be a problem with the patched version of your game, i dont think its a problem with the nationality of your game; i've played a few american demos on mine and mines australian.
What you need to check when the errors come up is what version the demos is, it should have four numbers somewhere, "network protocol XXXX outdated, current version is YYYY." Remember both numbers.
Go to steamapps/common/L4D2/L4D2, there should be a notepad file called 'steam'. Open it and change the network version to the patch of the demo (XXXX).
Now you can play it, but if you want to leave memory lane and play the game online with ppl in the present
, you gotta change the number back to 'YYYY'.
Pre-dlc demos arent viewable though, idk why.
Isn't valve silly? :>
Edited once, 12/4/11 - 7:38pm.
Posted on Tuesday, 12th April 2011