Hi. Perhaps I can help. I’ve made it work in IE8 – the PIE documentation states that the element to which the properties (rounded corners, box shadows, gradients etc) should be assigned should be given a relative/absolute/fixed position, and a z-index.
Secondly, I noticed that the extension .htc works locally, but to be able to see it on a server, one should use the extension .php.
P.S: It’s a little weird but I’ve used .htc here, and it seems to work in IE8, but to make it work even in IE9, you’ll have to use .php. (the .htc extension did not work in another project that I had worked on)