Hi Joe,
I "fixed" it but it just makes another problem visible. When you have events that span accross days, it is done with a td that uses a colspan and that td will get the background color of whetever kind of day it starts on (ie weekend, weekday, other month, current day), so even with the fix, if you use the rounded corners you are going to see the background color of the td.
I guess it will look ok for events that don't span days and the fix doesn't cause any problems when not using rounding so I guess its ok to make that change, it just won't be a perfect solution.
Best,
Joe