The problem, when it occurs, is intermittent. Your best option is to upgrade to version 6.0.8.2273, on which, during my own testing, I have not seen this problem (and which certainly fixes known related issues)
6.0.8 has just been released, and unfortunately problems with installing it over 6.0.7. have been reported. I suggest that you uninstall 6.0.7. and delete the Task List file (details in the FAQ) before installing 6.0.8.
David