Comment 4 for bug 1218333

Attaching far simpler test case: a circle (r = 200 px) in the center of the page (default document)

Steps:
0) launch inkscape with default prefs, open attached file
1) select circle at the bottom of the stack
2) duplicate it (change fill color for better visibility)
3) apply 'Path > Inset'
4) switch to the node tool to visualize the nodes of the inset path

Above steps work quite ok with r12419, but with r12420 and later revisions, the resulting inset path is quite unexpected (and not really useable).