(I'm on Windows 7, Maya 2015 SP6) I have no idea when did this start, but recently all newly created beziers have their tangents broken by default. The creation tool worked properly (both the Bezier and the Curve-3 Bezier tools), but once the tool's completed, all the tangents break. Using the Smooth Tangents option on…
I was seeing this problem as well. Didn't want to delete my prefs so spent like 1.5 hours combing through my prefs file, deleting stuff and testing. Ended up discovering that deleting the lines related to symmetric modelling fixed the problem. I think basically you just can't have symmetry enabled when editing a bezier…
Nuked my userPrefs.mel file and got it working again. Tried to find which property/setting was the exact cause, but after looking at the long list I noped out.