Excavator ~ I just tried to increase the z-index from 20 to 200 and even 2000 and the tool tip is still being cut off in IE7... you did check it out in IE7 right?
Also, although yes there are validation problems, the validation problems are not from any of the markup or css I wrote, but rather are from jsfiddle.net's markup set-up stuff. Even if I set-up an empty document like this: http://www.devinrolsen.com/calendar-problem.html
that is valid, this IE7 issue still remains.
Please tell me if you indeed did test that z-index change in IE7, cause I'm not seeing it. Also, if you had it working why did you not hit save and send me back the updated version?