I just bought Dawn of War Gold and all the others since Steam was having a sale, and I'm stuck on one of the missions. 
 
I'm playing the campaign, and got to the fourth mission, and they want me to send my assault marines and my artillery to take over this ork camp on the bottom of the cliff I'm on, so I send in the marines and they basically get raped, so I restarted and tried the artillery, which seems to only be able to shoot once, and then the little orange bar appears but then disappears about 1/5 way through and then starts up again, constantly. 
 
Is this a bug? And if it isn't, can you tell me what I'm doing wrong?

Yup, I'm bumping my thread. 
 
I feel dirty.