I hit this one yesterday and I was taken by it for a little while until I figured out how to kill this program to allow me to finish installing Adobe Flash Player 16 on a teacher's Mac.
Here is how the error goes. You are told by a website you need to update flash. You download flash, and start to install it. It gets done downloading and then when it goes to install it says you must stop this program. Flash Bridge-Wrapper-Crossplatform. You check again and all your program running flash are closed that you can tell.
The easy way to do this with out restarting or pulling hair out is to use the activity monitor to kill it the program. These instructions are for 10.9 mavericks but should be about the same on 10.6 and up as of right now.
Open spotlight (spy glass icon in top right on most macs) and search for "activity" (no quotes). Select "activity monitor" and run it. I like to put in abc order by hitting bar above the program name, but you don't need to. Find Flash Bridge and click on it to highlight/select it then hit the button in the top left of the window that looks like a stop sign. Wait a few seconds for it die and then you should be able to continue to update Flash Player.
I hope this has helped you get thing going back on your Mac and as always thanks for reading I hope I was able to help.
