Reproduced in SONAR X1, X2 and 8.5.
Open a new SONAR project and insert EZkeys in a simple instrument track. Do not include any audio or midi in the SONAR tracks.
Do not insert any midi in EZKeys. Set EZK to Follow Host. Set a looped section from measure 1 - 4. Press play. Expected a looped section of silence. What I got was a SONAR crash in all versions.
To prevent a crash all I needed to do was to insert midi into the EZKeys songtrack or place a midi clip in the SONAR midi track.
I've submitted a similar report to Toontrack.