It seems JSBuilder fails on a valid regular expression. I am trying to compress the Dav Glass YUI Addon Tools.js and I get an unterminated string literal error from JSMin on the following line:

syntaxCheck: /^("(\\.|[^"\\\n\r])*?"|[,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t])+?$/
(notice the odd number of double quotes)

BTW, Jack thank you so much for yui-ext and the JS Builder tool -- they have been a huge help for me.