I've been trying to track down why Air recently stopped responding on certain pages in my Ajax app. I tracked it down to instances where I used -webkit-box-shadow on large elements on a page. It seems to work ok when used on small popup windows, but if I use it on a large table or div (around 1000px and up), Air becomes painfully slow and occasionally stops responding. I went through and commented out all of the shadows and everything is okay again. Only happens to the Windows version. Tested on Windows 7 and OSX 10.6. Not a problem when using webkit based browsers.
-webkit-box-shadow: 3px 6px 10px rgba(0, 0, 0, 0.25);