Sometime in the last day or two I've noticed the tag previews no longer show up.
Previously, I'd be able to type in tags and see the tags show up underneath, allowing me to double-check my tag choices by hovering over them and getting the tooltip. But as I write this, I am not seeing any tags for this question. Nor did I see tags update when I was filing a suggested edit that retagged a question.
Typing out this question shows me this:
Suggesting a retag shows me this:
I've reproduced on Windows 7: IE 8, FF5, Chrome, and on OS 10.6.8/Safari (5.0.5).
Update After playing around some more with FF5, IE8, and Chrome on Windows 7, I seem to have this issue when I'm logged in. If I turn on private mode and try to do stuff anonymously, I see the tag previews as normal. I've tried clearing cache and browser history, and even tried browsers that haven't visited this site before to no avail.