If I change the month and/or the year the datepicker closes.
Only with IE8.
works for me on demo http://demo.piwik.org
can you see the issue there as well? it's running 0.7-rc1 but I dont think this code has changed since your version.
doesn't work for me using ie8 on win7.
@matt: yes, problem exits there, too. IE8 & Win7.