I have noticed this since upgrading to Lion.
Many times I accidentally use the pinch to zoom feature on the trackpad for Safari. Safari will zoom in a bit, but then the entire tab becomes frozen. No buttons or hyperlinks work, if you enter a new address into the address bar it will load, but it won't show up, etc. The only solution is to close Safari and reopen it.
Others have reported similar problems here
http://forum.notebookreview.com/apple-mac-os-x/634076-safari-causes-pinch-zoom-freeze.html
https://discussions.apple.com/thread/3196200?start=0&tstart=0
I have no extensions installed.
Best Answer
Not sure I like it, but I think it's by design. I don't really use the zoom function, but occassionaly activate it by accident when srolling. When you zoon in, it seems to remove all navigation functions other than scrolling or further zoom operations. You need to zoom back out in order to get it all back, however due to either inertia or some other feature it's possible for you to sort of bounce in again and zoom in a small amount again, making it seem unresponsive. It's very subtle, especially as the text will render beatutifully. So, in short, zoom out, check that you have really actually zoomed out all the way, then try again.