I had this same issue as well (I think it's the same issue).
Check your logs (if enabled) for an error involving the BeginDate function in /lib/Application/Schedule/DailyLayout.php ("Call to a member function BeginDate() on a non-object...").
This file has a loop that will go out of bounds if your schedule has a certain layout.
I changed the line (about 152):
while ($i < count($periods) && $tempPeriod->BeginDate()->LessThan($nextPeriodTime))
to prevent this error. I don't know if this is the best way to fix the issue, but it worked for me (at least as far as I can tell).