[cheekypaul]

I suspect your problem is this...
One of your plugins you are using is "spiking".
By this I mean that the audio signal created by going through the plug in, fx or eq or vi (anyone, don't know which one), has caused some kind of super low or super high click. This in turn "ruins" the channel.
When this happens you lose sound not connection.
Very common with GRM tools and Reaktor, when you push them to their limits.

To solve try these ideas...

Duplicate the channel, delete the old one.
Try toggling through the playback buffer etc, in the hardware drop down menu (though i suspect this will crash the system)
Save the setting of the PlugIn, delete channel, quit, reopen and reinsert on new channel.

Pro Tools has done this for as long as I care to remember, so don't panic.