i have a strange behavior and i'm not that shure that's a bug, but could be ...

i have several appointments - some has start- and endtime in the morning, some in the afternoon. but all are over several days:
starttime: 2007-01-01 14:33
endtime:  2007-01-16 18:33

it occurs sometimes (not always): i click on an appointment which has his start- and endtime in the afternoon the appointment moves to the next day.
this problem occurs only on afternoon-appointments.