Hey mate, I’m not sure if this will help but I literally just made the same mistake. Whilst having a mess around in the settings I accidentally changed the root url and after that everything wen haywire. I host my site off Crazy Domains, which does accompany the phpMyAdmin thingy-majig. I had never even heard of it until a couple minutes ago, and everything if fixed now, which proves to show how easy it is. Just incase you missed the instructions on the Codex:
1. Backup your database and save the copy off-site.
2. Login to phpMyAdmin.
3. Click the link to your Databases.
4. A list of your databases will appear. Choose the one that is your WordPress database.
5. All the tables in your database will appear on the screen.
6. From the list, look for wp_options. Note: The table prefix of wp_ may be different if you changed it when installing.
7. Click on the small icon indicated as Browse.
8. A screen will open with a list of the fields within the wp_options table.
9. Under the field option_name, scroll down and look for siteurl.
10. Click the Edit Field icon which usually is found at the far left at the beginning of the row.
11. The Edit Field window will appear.
12. In the input box for option_value, carefully change the URL information to the new address.
13. Verify this is correct and click Go to save the information.
14. You should be returned to your wp-options table.
15. Look for the home field in the table and click Edit Field. Note There are several pages of tables inside wp_options. Look for the > symbol to page through them.
16. In the input box for option_value, carefully change the URL information to the new address.
17. Verify this is correct and click Go to save the information.
18. Delete the folder wp-content/cache (this is a new folder added with WordPress 2.0).
19. That is it.
