Error in L4D2

[Shyria Dracnoir]

Whenever I try to pull up The Passing campaign in single player mode, the loading screen progresses normally, but right before it starts my game shuts down completely and gives me an error message that looks like this:

5/-survivor_bot: UTIL_SetModel: not precached: models/survivors/survivor_biker.mdl

I'm no programmer, but I'm guessing it has to do with problems loading the bot survivors (pretty obviously Francis from the nickname, though once it gave me something else right at the end that I didn't write down. I've gotten this version twice though). One of my friends just gave me a bunch of custom maps and textures the other day, and the first time I noticed this error was after I put them in (copy/pasted from a portable harddrive into the addons folder) though it might be the problem's been around for longer and me checking then was a coincidence. Any thoughts?

EDIT: I've been able to join games in Online Campaigns just fine, though I haven't tried starting one myself (and booting up Versus might be moot since the bots don't show up there anyways).

[Doc ock rokc]

I think that the Francis model in your game isn't given a valid location at the very beginning. thus the crash.
try deleting and re-downloading the files.
Or you could try Submitting a bug report to valve and follow your advice.

[Viridis]

I did a little searching and the problem does seem to be caused by the Passing not being compatible with some addons.

Something about custom population.txt files.

Here are some of the addons that don't work:
cursedtrain.vpk = 29,572KB
deadairmodifiedv4.0.vpk = 5,047KB
dead air.vpk = 239,561KB
deathtollmodified3.1.vpk = 13,212KB
Gauntlet.vpk = 81,955KB
infectedforl4d1maps.vpk = 10KB
nmmodifiedv7.0.vpk = 33,638KB
no_mercy_2.vpk = 157,455KB
The Passing Update issues - Steam Forums (http://forums.steampowered.com/forums/showthread.php?p=14683401)

[Shyria Dracnoir]

Thanks for the link, Virdis. It pretty much describes exactly what I've been experiencing. I'll go back through my custom campaign stuff and take out the bad stuff (I know deadairmodified was one, need to check on the others though).