If you are using Firefox, go here: https://www.mozilla.org/en-US/plugincheck/ and make sure that all of your plugins are up to date (especially JAVA). I believe this may help to alleviate any problems being had using Firefox. Also, it is a good idea to go into, on XP anyway, the add/remove programs and delete all of the old JAVA editions, leaving only the most current one.
Over three years on and I wanted to see if anyone in this thread still had trouble posting, possibly if their absence was due to access problems. There are a few solid members who posted in this thread with extensive posting histories that haven't stopped by of late. I might contact them directly to double check access.