I have been playing around with Google’s Web Accelerator and found that webmail at JH will not work when accelerated.
You must deactivate acceleration for the IP address of webmail, done in pefereneces settings of the tool.
I have this issue with a number of other sites that use sessions or require login as well. It is a good note to anyone using GWA that if you have an issue disable if for that site and give it a try.
Interestingly I have an issue with one tool I use all the time, if GWA is even ENABLED it wil just show the CSS code, I have to fully disable to even view the page.