widgets.php (blank page) and capabilities.php (no sufficient permissions) errors

As i was editing my blog yesterday a blank page appeared from nowhere and i havent seen my blog since. After a lot of searching i found this:

SQL-Query to reset widget sidebar configuration:
UPDATE wp_options SET option_name = CONCAT(‘debugbak_’, option_name) WHERE option_name = ‘sidebars_widgets’;

Using this coomand i was able to see my site again but when i click anything in my site the blank page reappears. I use the same command again and everything is ok until i click something. The error that im getting is about widgets.php. I used one more time the command above an i tried to log-in as admin in order to delete some plugins. As soon as i click the log in button this message appears:

“You do not have sufficient permissions to access this page.”

The error i get is about capabilities.php. I deleted everything in my server, including the database, i downloaded WordPress 2.6 one more time and i uploaded it to my server. I created a new database and i tried to view my blog. The installation page came up but my luck ended here. I had the exact same problems although i had a new installation. This is day 2 and i cant find a solution to my problem yet……..Any ideas before i burn my pc?