So I bought a Yamaha expression pedal. I'm using it set to modulation/CC1 plugged directly into my Virus TI2, in sequencer mode, running with Ableton Live on a Mac (latest software on everything).
Twice in the three or so hours of me playing with it, the Virus has gone "dead" to CC1 messages. That is: the pedal stops working, the mod wheel stops working, and the Virus stops responding to automation on that controller from Live. I can see that the Virus is still getting the messages, in that when a part is selected which has a soft knob mirroring the mod wheel, I can see the soft knob move on the Virus Control plug-in. But no audible changes can be produced by CC1. (I can still get responses to the mod wheel and pedal by changing them to another CC). So, in patches like that, I can move the mod wheel and watch the soft knob animate on the plug-in, but you can't hear any effect. If I grab the same knob and move it, it works properly.
To restore it, I need to shut down Live and reboot the Virus. Rebooting the Virus without quitting Live is insufficient.