If those do not work for you then we need to know
(1) how you are connecting to the internet and to WordPress.com? The way you connect to the internet (mobile, satellite, DSL, dial-up) and to your blog, and how many proxy server jumps etc. it takes to connect can cause problems. There maybe be problems with your ISP and/or with the proxy servers.
(2) Exactly which browser and version of it are you using. If you don’t know click here to find out > http://whatsmyuseragent.com/
(3) Have you tried clearing your browser cache and cookies? http://www.google.com/support/accounts/bin/answer.py?hl=en&answer=32050
(4) Have you tried using the browser with all extensions or add-ons disabled?