Datepicker bug: only 5 days in March 2011

Datepicker bug: only 5 days in March 2011

If you open the datepicker demo page on http://jqueryui.com/demos/datepicker open any single month view picker, and navigate to March 2011, it only shows the first 5 days on the month, but if you select a multiple months view it's fine.

I've tried it on two PCs: Windows XP-SP3 with IE6 and Firefox, and on Win7 with IE8,FF,Chrome. all showed the same bug.

The weird thing is it worked on another  XP-SP3 pc on both IE and Chrome.

Any Ideas?