I don't know if I'm being silly or broke a setting somewhere but I'm having strange problems slicing a part from http://www.thingiverse.com/thing:41967
I've run the part through netfabb basic which finds no problems.
This funny thing is that I have two identical parts on the build tray, but they are sliced differently.
Also, exiting preview mode and re-slicing produces different results every time...
I also don't know why there are gaps in the outside perimeter...