Sometime last year when this same topic came up, I wound up getting a reply after contacting AdSense directly through my account. While the problems were resolved quickly, it wasn't until I included links to their official forum in my email (see ThatsBoBo's comment above) that they realized there was a problem with the ads displaying correctly. I highly recommend contacting them through your account and/or continuing to comment on the official forum posts.
Is this issue resolved? Any updates from anybody? Yesterday I saw intermittent errors on IE6 but today no error in IE6 when checked 3-4 times. Just need idea whether this issue is sorted out by google.