Uncategriezed is the default acategory that's automatically assigned to any post we do not assign a category to. > http://en.support.wordpress.com/posts/categories/#setting-the-default-category
Clicking Edit under the name of a post will take you to the dashboard editor, where you can make changes. Please describe exactly happens what you try to edit the post in question?
1. There maybe be problems with your ISP and/or with the proxy servers. How are you 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.
2. Are you using http:// or https:// see http://en.support.wordpress.com/https/
3.Exactly which browser and version of it are you using? If you don’t know click here to find out > http://whatsmyuseragent.com/
4. Have you tried clearing your browser cache and cookies? http://www.google.com/support/accounts/bin/answer.py?hl=en&answer=32050
5. Is your browser version up to date? You can upgrade any browser version here. http://browsehappy.com/
6. Have you tried using the browser with all extensions or add-ons disabled?
7. Do you have third party cookies enabled? http://support.google.com/accounts/bin/answer.py?hl=en&answer=61416
9. Do you have another browser you can try?