**System Information**
Win 7 ult. x64 Sp1 + Nvidia GeForce 8800 GTS 512
**Blender Version**
Broken: 2.71
Worked: ?
**Short description of error**
The Knife tool (K) do not 'truly' follow angle constrain (C) after switching back and forth from perspective to orthogonal view (Numpad 5 x 2).
Screenshot available at http://imgur.com/8QuE9EE
**Exact steps for others to reproduce the error**
Open a new scene
Enter Edit mode with the default cube selected
Switch View Persp/Ortho at least once to orthographic view (Numpad 5)
Switch back to Perspective view (Numpad 5)
Use Knife tool (K) with angle constrain activated (C)