Phil - yes, MYOB
I have moved the Syncdocs folder away from the All Users shared directory (I only specified this because MYOB compelled the use of this directory until the recent service pack release). Syncdocs seems to be working better but it is still updating while open.
Apart from the crashing issue, syncing while open is still not ideal as even pushing out the time tolerance to 300 seconds results in a large number of uploads of (potentially) large files during a given day.
I have found extending the time tolerance is extremely dangerous, as saving the file within the time tolerance can result in the Google Docs version not being the most up-to-date version - if this is then synced with a second computer, there is every opportunity for changes in the original file to be missed.
If syncing-while-open can't be stopped, other alternative is to have syncs happening regularly, say every 30 minutes - is this a potential feature?