Drawing 3 point arcs from time to time leads to a result as if the 3 points had been clicked in a different order, giving you the "wrong" section of the arc (I don't know what are the right conditions that determine this behavior, but I attached an example file).
This is an ancient bug in CU that never has been resolved.
The workaround is to draw a 3 point circle and trim it, but I think CU should be able to do better than this, shouldn't it?

Ciao, Norbert

Hi Tim.

You're correct, it's the "Three Point Arc" tool (Start, Pt On, End).
It is a bit difficult to repeat the behavior, it just happens from time to time.
I used to think it dependet on the position of the points, but a quick test with the file I attached disproved this assumption: this time it worked perfectly fine.

But I can confirm that the described bug happens quite frequently. It seems to occur in a way similar to some other CU "strange behaviors" like:
Copy and Paste greyed out (in older versions, now resolved) "redo" command going away and the notorious "snaps stop working" (see: [URL="http://forum.punchcad.com/showthread.php?t=393"]http://forum.punchcad.com/showthread.php?t=393[/URL] - please have a look at this one - it is driving me nuts!)

The 3 point arc problem goes back to at least Version 3 (of Concepts 3D at that time).

Ciao, Norbert