I had the same problem and then I figured out that the Artemis bulbs are shorter and weren't making the contact they needed to in my lights.  I tried the 150W and the 70W MH bulbs and both are a bust. When I e-mailed them, they told me that I must be mistaken as no-one else had a problem. 
 
Gone back to the plusrite's form LSE on E-bay.  Great bulbs for a great price. 
		
	
		
		
		
		
			
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				Mark...
  
290g Peninsula Display, 425g total volume.  Setup Jan 2013.
			  
		
		
		
		
	
		
		
	
	
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