I've got a client that launched their site a few weeks ago. Yesterday the client calls and claims that some of their IE6 viewers are unable to view the PNG files embedded into the page.
We QA'd on 7 PC's with IE6 installed and were not able to duplicate the issue as the PNG fix was working properly for us. We asked the client to come in and he did but as described the PNG files were not showing up for him on his browser using "IETester" to see it in IE 6 rendering.
I explained to him that it could be related to the fact that he is not using a true standalone version of IE6. Problem is - we downloaded IE Tester and had no problems with the PNG's.
I'm beginning to think that somehow the issue may be related to some OS or hardware problem. I made a simple png on background test page with the standard PNGFix and nothing else and we were unsuccessful getting the PNG to display for him.