I am getting this problem too. To duplicate, you need to have the datepicker's selected value be in the first week of the month AND that month needs to include at least one grayed out day from the previous month in the first row (in other words, a month where the 1st is not on Sunday). If you bring up the calendar and click the previous month button, the calendar closes. Likewise, if you set the datepicker to a date in the last week of the month, and the last week has at least one grayed out day from the next month (last day of month is not a Saturday), and you click the next month button, the calendar closes. Originally I was getting this bug in 3.1, so today I upgraded to the latest 3.7 version, and it's still happening for me with the new version.