If you apply border images to a table using PIE it has trouble when you scroll. The border images start jumping around. A quick search of the forums netted no answers, so I delved into the source and found the solution. I'm not sure what else this might break, but it certainly fixed my site (in IE8). So I'll post it to help others with the same problem and perhaps it'll get integrated into the main code.

The problem is on line 2155 of the latest PIE_Uncompressed.htc

By default the line is like this:
docEl = doc.documentElement;

However, if you change it to this, everything starts working:
docEl = doc.body;

It seems that scrollTop and clientTop are properties of the body, not the document. I'm not an expert on this, so maybe this is a change in IE8? Or maybe its just always been a bug, but its rare to fall back to the document level with these things?

Anyway, its also easy enough to changed in the compressed version to. Search for doc.documentElement. Find the SECOND hit, then replace it with doc.body. I would attach a modified version of the file, but I'm not sure if that is allowed.

Thank you for the investigation. I'll give your fix a try and make sure it works across versions.