Just a thought, I believe if you have (2) 8-ohm speakers wired in parallel, that essentially creates 1 4-ohm speaker going into the amp. When you bridge an amp, it drops it's ohm load to half. So in theory, your amp will be producing a 2 ohm load, and if it is not 2-ohm load stable in bridged mode, clipping or cutting off(shutting down) can happen.

 

Your about half right yes your are essentially creating 1 4 ohm speaker. Bottom line. If you have a 4 ohm load and are running bridged then the amp has to be 4 ohm stable bridged. That is it plain and simple. I think I confused people more then helping. So hopefully this clears things up.

Here is a good tutorial:
http://www.elitecaraudio.com/article.php?sid=105