Yeah, sorry. I shouldn't have made that post so useless.
Yeah, it was TF2.
It's still giving the unknown command, but with a different error:
L 07/23/2008 - 00:24:47: [SM] Plugin encountered error 15: Array index is out of bounds
L 07/23/2008 - 00:24:47: [SM] Displaying call stack trace for plugin "sm_sethealth.smx":
L 07/23/2008 - 00:24:47: [SM]  Line 74, /home/groups/alliedmodders/forums/files/3/9/2/6/9/29157.attach::Command_SetHealth()
If you need a server to test on, I wouldn't mind letting you use our TF2 server.
EDIT: Seems it's only the engineer that gives me the unknown command. All the other classes work fine.