Webplayer issues on a MAC - Player keeps moving

I made a Webplayer build and everything works as expected on a PC. However, on a MAC the directional controls (arrows or WASD) do not respond until the mouse pad is touched, and then the player continues to move as if the directional keys were still being depressed. The user can change directions by touching any directional key, but the player continues to move at full speed even when no directional key is touched. I removed all my scripts and the problem remains.

These same computers work as expected when I make a MAC (non-webplayer) build. I need to release my program using the Unity webplayer for both PCs and MACs.

Is this a known bug with the Webplayer and MAC? Is there a workaround or solution?