Linux bubastis 3.10.25-gentoo #10 SMP Thu Jan 30 22:17:35 UTC 2014 x86_64 Intel(R) Core(TM) i7-4800MQ CPU @ 2.70GHz GenuineIntel GNU/Linux
01:00.0 VGA compatible controller: NVIDIA Corporation GK107GLM [Quadro K1100M] (rev a1) (prog-if 00 [VGA controller])
Broken: git 2c69f1e574587c2364e9a94b45d0b363ffeebf61
Short description of error
If a curve object consists of multiple independent bezier splines none of which are closed they are visible as 1-pixel curves in the UI.
If you change one of them to closed (use_cyclic_u=True) then the closed curves are not visible in the UI unless the object is selected or active.
To reproduce the bug create a curve and create two splines within the curve.
Make one spline closed and the other not closed.
Have the curve panel open with the Active Spline cyclic checkbox visible.
Make sure you are in object mode.
toggle the cyclic checkbox repeatedly and watch how the unclosed elements of the curve disappear and reappear from the UI.