Bug in extrude? ( Possibly just a display bug ).

 From:  Colin
313.5 In reply to 313.4 
Hi Michael,

Thanks for that, I kind of figured it'd be something simple that I'd done!!
Especially as I could Extrude the top section with out any problems.
In future, I'll try to keep an eye out for those pesky duplicate points :)
Any advice on how I'd be able to track them down, should something similar happen again?

regards Colin