I wrote a simple timepicker widget and found what seems to be a bug with the scroll container in chrome. When you click on the clock button on the timepicker, a white box covers the majority of the window. I've reproduced the bug in this jsfiddle: http://jsfiddle.net/WX4fR/
It has a temporary css workaround commented out.
I've run into this problem on other views as well. It seems to happen inconsistently with different window dimensions and not specifically with the timepicker widget. My current chrome version is 21.0.1180.60.