Marching Ants Acting Strangely

1)     Use the pen tool to make a rectangle - in the layer panel - Paths - Command Click and the marching ants make a rectangle with rounded edges.

2)     Use the pen tool to make a triangle - Command Click the marching ants make a egg shape.

3).      I have unchecked Preferences - Performance - Use Graphics Processor and restarted photoshop - problem not solved.

4)       I have checked that the upper case key isn't on and as far as I can see there is no reason why this should suddenly start happening. 

Does anyone have any suggestions?  I'm trying to make some mock ups and this problem is holding up the process.  All help very much

appreciated.

Thank you.