Bad / invalid cd key?

i have a some unbanned Arma 2 oa keys.
Checked them with darky's and they are unbanned.
But when i try to play with them i get the message:
Bad / invalid cd key!

50% of the keys got this message the other 50% is playable

Anyone knows how to solve this?

thanks.

Invalid CD Key, check this with Darky Key changer

Now i can see which one is invalid and which one is not,
Anyway to fix the invalid keys?

Maybe a keystealer fucked up your reg? Try doing some of the usual fixes. I once had an error like you with all clean and legit keys. I deleted the registry folder and validated local files at steam. That should maybe work

My registery is fine and my pc is keystealer safe.
I think it has something to do with the keys? and i didnt find any sulution yet on google or forums.

When i sold some keys to someone i checked them if they were banned and they weren't.
some people said that the keys were not working (invalid / bad cdkey) so i provided them with a new one, and checked the key they said that didnt work..
Guess what? I Also got the same message: invalid / bad cd key

anyone else with the same problem and a solution?
thankss