Deformation manipulators won't always show?

So far, to show a controller on a deformation, I click on the peg, make sure show simplified manipulators in on. Then select “Show selected deformers and hide all others”

Sometimes it works, sometimes I just can’t seem to show the manipulators…

Any Idea why, or what I’m doing wrong?

Oh and If just save, and restart the program, it’ll work. So is it just a program glitch?

Thanks for any help.

When I have a lot of programs open and am working on a heavy scene this can
happen sometimes when my graphic card is overtaxed. Generally if I close stuff
and re-open the program it fixes it but I have also had to reboot to regain graphic
card resources.