Every once in a while I'm happily editing drums in Piano Roll and all of a sudden when I draw a new note I get this crazy complete drum pattern playing, at not even at the tempo,, it's sort of like all at once a 3 minute track playing in 3 seconds? 
Anyone else? 
Only thing I have verified is that projects that do this have session drummer and a pattern loaded, I don't use the patterns but they seem to load with certain pre set kits. how do you delete them if that's the issue? Build a new kit from scratch seem the only way to delete the pattern box. 
 

MIDI notes 27 through 34 play MIDI patterns A-H respectively. Note 24 turns off patterns. This is a feature of Session Drummer. See the Session Drummer help file "Using MIDI PAtterns" section for more information.

Thanks Steve, I bet what happens is notes are being accidentally drawn on those values you mentioned. The new default piano roll view will be to blame as it has become very narrow and only shows a small piece of the whole, I just recently have been messing with floating it over to my second monitor. I do miss the old 8.5 view. 

johnnyV
The new default piano roll view will be to blame as it has become very narrow and only shows a small piece of the whole

The Piano Roll View can fill the entire screen. When the PRV is docked "D" and "SHIFT-D" may be the shortcuts you need.  This thread http://forum.cakewalk.com/FindPost/3100719  describes another way the view can be maximized in SONAR. See my post #7 for the steps. Screensets are another way to display a larger version of the PRV.

Yes, thanks, I read that and that's why I'm heading in that direction, It's just as you know in 8.5 all we did was click the track and were good to go. It's just a lot more work now to regain that same view. Not complaining it's just old habits die slowly round these parts.
Idiots like me just keep working and don't often take the time to learn the new features right away. It's only been since February so all in good time I'm getting there. 
And I even bought Scott's book! 
 

It can be a single click on the clip in X3 too. One thing I believe many familiar with Pre-X series SONAR do is close the PRV instead of minimizing it with keyboard shortcut "D". The first clip opened in the PRV needs "SHIFT-D" to maximize the PRV. Then instead of closing the PRV use "D" to minimize it. The next time a clip is clicked, the PRV will open maximized.

That's about it, as I say old habits. It's hard to teach old dogs.. :>