Hey sharke... I found one of the very first projects I used Geist with, and verified scook's advice is on the money. I also had inserted Geist as a SIT, and simply right clicked that track and selected "Split Instrument Track," right clicked on the MIDI track to open the piano roll view and inserted a note randomly way out near the end. After that I simply frozen the MIDI track, and it worked fine. (I also do not freeze tracks often, but have not stress-tested Geist capabilities (yet).)
Since you are using engines within Geist, I am "assuming" your MIDI track is totally empty (otherwise it would double-fire notes), so scook's advice above it probably the answer for you.