I've tried looking around without success, but recently (as in since the upgrade to 14.04) I'm noticing that if a set up a play list with multiple video files on any player the screen automatically locks after the end of the first file. it didn't used to. is there a way to set this so I still have the lock on, but can play more than one file without the screen going black and locking me out after the end of each file?
Thanks!

Can you explain what you mean by that?
No further videos play?
The window manager becomes unresponsive?
You can play an additional video in the current video player but you have to load it manually?

the screen is set to lock after 10 minutes of inactivity. if the first video is longer than the 10 minute timeout, the screen locks normally at the end of the video. everything works as it should, the videos keep playing but the screen goes black. I have to either move the mouse, or the screen locks. this is a bit of a hassle if I'm watching a bunch of short videos and don't want to have to keep running over to the desk and keep moving the mouse every time a video ends. I'm trying to watch a set of educational videos, and for the most part they're around 30 minutes each. I'd like to be able to sit across the room if I can without having to get up every 30 minutes and move the mouse.
thanks for your help with this,

I'm not sure how you do this in Ubuntu but in Slackware it's a pretty trivial thing to reset the screen lock to something higher than thirty minutes.
The other two options I can think of are to create a script that randomly moves the mouse in 29 minute schedule or the inputs a key punch...
...for example. You can check xev for a key on your keyboard that does something similar and write a wrapper to run the cron'd script every time you start your video player.

this still doesn't adress the issue. often I have several files. sometimes equalling 3 or 4 hours. in the past it didn't go the screensaver mode between files, now it does. I don't want to have to keep adjusting my settings everytime I create a playlist, I want it to be like it used to be in the past where as long as the player was playing files, it simply didn't go black. I think it's when they moved away from having screen savers and went to this new lock thing. they've apparently overlooked this simple issue. I was just hoping there was a simple fix.