Concat datetime64 bug

[wesm]

dr = pandas.date_range('2011/1/1', '2012/1/1', freq='W-FRI')
a = pandas.DataFrame()
c = pandas.DataFrame({'A': 'foo', 'B': dr}, index=dr)
a.append(c)

[wesm]

this fails:

dr = pandas.date_range('2011/1/1', '2012/1/1', freq='W-FRI')
ts = pandas.TimeSeries(dr)
d = pandas.DataFrame({'A': 'foo', 'B': ts}, index=dr)