When ks-1.3 was upgraded to Rice 2.2.0, we found that all of our devs and testers had to manually clear their browser caches, because the Rice upgrade depended upon changes in the JS files that were not being pulled in due to caching.
Garey mentioned this in the KS Devs as a possible way to handle this:
[5/21/2012 10:07:10 AM] Garey: Yeah, it's caching. So, with the Rice upgrade I think some of the underlying js files were changed. JS files are permanently cached. GWT got around this by generating all js file names at compile time based off of a hash code, which ensured you never used stale / cached classes.
[5/21/2012 10:08:08 AM] Garey: Note: this will be a a BIG pain for users in the future.