I just started a new site several days ago, but I have worked in wordpress before. I have never since installation been able to use the widget admin page (as far as I know). The site is mavenmatt.com.
I have read forums for 3 days and here are all of the things I have tried and didn't work (everything I can remember):
1)Deactivating and/or reactivating all plugins.
2)Deleting and reinstalling all plugins
3)Deactivating plugins in PHPmyAdmin and reactivating
5)Downloading new wordpress files
6)Deleting and replacing the widgets.php file with a new one
7)Installing the Use Google Libraries plugin
9)Adding new "define" codes to wp-config.php
10)Clicking on "Screen options" on the widgets page (also not working)
11)Check multiple browsers - I have used Chrome 10, IE9, and Firefox14.
12)Wait a day
13)Undo/Reset other changes in WP Admin
14)Read every forum post I can find on the issue (and maybe some more things that I am missing).