I am playing it in Arma2CO.
I was just in editor creating personal missions to play and all of sudden when I was done for time being and decided to play the said mission, that error came up.
Edit: I checked the COSLX folder and it contains all three SLX_NetCode, SLX_Shout
,and SLX_wounds.pbo. Edit again: Error still continues even with the needed scrips/.pbo's.