Sure. The example I was thinking of in particular was an internal project from about 5 years ago where their CSS2 layout completely blew up on IE6. However rather than get down-n-dirty to fix it, they demanded additional budget for a rewrite using tables.
But just last week, another subcontractor apparently didn't realize that our government client was stuck on Flash v9 and spent the next two weeks trying to sort it out.
And it hasn't happened in a few months, but we used to get occasional complaints from clients stuck on Safari v4.
