"no client" This  keeps randomly popping up no matter what screen I'm on.  It started after the kitkat updates. Any ideas on what this is ?

I'm new to tablets and have download Nexus Media player. Here's the problems I'm having. I use a Casio Ex Fh-25 for filming my kids sports in HD or high speed video 120 or 240 fps. Ive tried Mx and Bs free apps but when I try to play it back on the Nexus 7 it's choppy or stops the video. It says Avi if that matters at all. Am I doing something wrong here or is there a better free of pay app that I can use? Any help would be appreciated . Thx Larry