I'm stuck on Mission 10 of Crusader: No Remorse. The objective of Level 10 is to destroy Dr. Hoffman's cloning operation. I have found two green keycards, but I still get ACCESS DENIED INVALID KEYCARD whenever I try to open the door with a green card slot which leads to the Waste Disposal area. One of the green cards came from a dead doctor is Incubation Area #1A (or near there), and another one came from some barrels near Cloning Area #4A (or whatever). The door I'm trying to bypass has the number 1 on the adjacent walls. Can anyone help me?

There's a cluebook available here:
http://www.pixsoriginadventures.co.uk/downloads/

Not sure through looking at it exactly where you are at the moment, but hopefully the maps provide some useful information.

Alternatively, it's sometimes possible to blow doors open with the grenade launcher or a detpac.

Thank you for posting this link. Very helpful.
I've managed to finish that mission, and the entire game now for that matter.