http://www.quirksmode.org/bugreports/archives/safari/index.html "When you place a display inline on a fieldset and the form elements within the fieldset are floated, the form elements wont be clickable by Safari. Using a position relative will fix this. Test page http://www.xs4all.nl/~blackeye/safari_bug.html Workaround is included Reported by: Paul van Steenoven."
Fixed in latest nightly. Closing as worksforme