I might have found a solution:
I am new here, so take everything I say with a grain of salt.
I just installed Beta 2 and had similar performance issues.....loading of the inbox and other folders was extremely slow, even with only few messages. The setup, in my case, can not be the issue, since IMAP, mySQL and RC are on the same server, so queries should be rather quick.
The problem, I think, was with the rendering of PNG files (and the additional scripting, that is in place to make transparencies work in IE 5/6). I replaced the key icons
- dot.png
- attachment.png
- unread.png
with GIFs and it now works much, much faster. The lists loads almost instantaneously.
It's a bit of an ugly hack: in order to avoid needing to do too much coding, I saved the GIFs with a .png extension....not pretty, but IE renders it correclty, and I think most browsers should do so, too.
I attache the three icons for anyone who would also like to try this....let me know whether it also works for you.
(P.S: Please note that the icons are slightly modified from the originals to adjust for lower color depth etc.)