Staff not being displayed correctly - Sonar 8.5.3

[revnice1]

See pic. For no apparent reason, notes in the Staff View began to clump together as though I had the wrong snap value set. I didn't, the correct value (1/8th) and even a 16th was set but the notes snap into each other. The pic shows kick drum hits on a MIDI track which are actually 1/8th apart but they appear to be placed at the same point in time. The software is Sonar 8.5.3 (the revered version) and I've never seen this before.

Has anyone seen it before and does anyone know how to fix it?

Thanks - rev