I came across this column sizing weirdness the other day.
Using a RadGrid the headers looked great. The rows with the data however sized
however they felt like it, usually way too small. After looking around I came
across this that solved my problem. Adding the meta tag of <meta
http-equiv="X-UA-Compatible" content="IE=EmulateIE7" /> in the head section
of my aspx page was what I needed.
My issue was pretty specific since I had to target IE8 for the app I was
working on but it may apply to other scenarios as well.