parallel video playing problem

I've recently encountred a problem while using a thunderbolt to connect my mbp 13 (i5 early 2011) to my iMac (21 i7 late 2011) -

While playing a video on my mbp using screen share mode to my iMac, pressing "pause" through a remote control activated a background player on my original iMac drive.

The only way, naturally, to stop the background play was exiting the screen-sharing mode, quit all programs on my iMac, and resume screen sharing.

Does anyone know - ***?