Hi screwdriverone,
I did a quick google for "catadioptric short tube newt collimation" and got some interesting results ... its seems you're not alone. Looks like some potential "mounting/squareness" issues with the internal barlow mechanim according to the first 2 Google results.
http://en.allexperts.com/q/Astronomy...elescope-1.htm
http://cs.astronomy.com/asycs/forums...50.aspx#304750
Hope this helps.