to all of you having problems playing online, try using the tunngle.net program to create a "virtual network" with each other or use it to host your own lan/sp server. it creats a virtual ip for your pc, so "invalid/in-use" cd-keys become void.
and as for the AI-Allies trick, try adding "human/survivor" bots to the .cfg file with classes, I know it sounds like alot of work but with time and patients, it can be achieved
K838
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