I was having issues with midi echo becoming enabled when I didn't want it. What I found was that selecting a VSTI in the synth rack would change the track view focus to the midi channel that was feeding the soft synth. When the related midi track got focus, the echo button for that track would be enabled.
 
Was it always like that or is it something new? It forces me to turn off echo every time I look at the synth in the synth rack.

I don't know but when I try auditioning sounds in Kontakt wit multiple instruments I hear them all. This is new and started in X2 at least I think it did. I haven't looked into as much as I should but it is an annoyance. 

disable Preferences > MIDI > Playback and Recording "Always Echo Current MIDI Track"

There is a setting in the Preference menu. Just un-select 'echo current midi track.' It's called something close o that.
 
CJ

I ran into this when I first installed X3. I've always had the echo preference disabled, but the setting didn#t get carried over from my X2 install. Confused the hell out of me at first.

Doh!
 
Thanks guys, I must have had a brain cloud.

This one got me as well. I'm sure the default must have changed.