You are right. There is almost no difference in the styling. What I tested next, was to skip the
call and to just test the HTML itself. I tried putting a regular file input field inside your k-upload-button class:
"filter: alpha(opacity=0) !important;"
This reproduces the issue. However, when the <div> is removed, the input field is correctly transparent.
After some research, I found out that the DOCTYPE has an effect on alpha filters and also that IE8 requires the following CSS:
Yet none of all this works. Since the Telerik example does work, it must be one of those obscure, unexplicable IE-specific bugs. I will retest this later for the next release. Maybe you can check the basic upload example from your website in IE8 for your latest development version, to see if there are any issues?