resetting wordpress?

how do I uninstall my theme? Basically, I want to start fresh!

Short version: use your ftp client or the file manager in your hosts control panel to remove the theme that is causing you problems, allowing wordpress to fall back to the default theme.

Slightly longer version:

Your posts are actually stored in the database. If you ever need to replace wordpress files, all of your content should remain intact. The exception would be anything in the /wp-content/uploads directories. That is where your uploaded media are stored. /wp-content also contains themes and plugins, so be cautious when considering replacement. You should always keep a known good working backup copy of your files and database.

If the only edits you have been doing are within the theme files, you can simply delete the theme, and if necessary, re-upload a fresh copy of the default theme from the current wordpress package. If you can’t log in because of a theme that is currently activated, you can use your ftp client to delete the active theme, then go back to //yoursite.com/wp-admin and log in. Once you do, the default theme (twentyten) should activate itself and restore control to you.

I deleted the bad theme and now my blog page is completely blank. There’s nothing on it at all, as if wordpress isn’t even installed. The TwentyTen theme is still in my ftp but no themes I had installed are apperaring in my dashboard…

Any further advice?

Nevermind, it did revert to TwentyTen. But all the errors are still appearing in my dashboard.

For instance, on my main dashboard page:
Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/averyxxx/public_html/blog/wp-includes/theme.php on line 519

And on my themes page:

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/averyxxx/public_html/blog/wp-includes/theme.php on line 519

Warning: uksort() [function.uksort]: The argument should be an array in /home/averyxxx/public_html/blog/wp-admin/includes/class-wp-themes-list-table.php on line 49

Warning: array_slice() expects parameter 1 to be array, boolean given in /home/averyxxx/public_html/blog/wp-admin/includes/class-wp-themes-list-table.php on line 56

Is there a way to fix these? Also, no themes appear in my theme section. And I can not upgrade to 3.1.3 because I get an error when unpacking.

Any help is greatly appreciated.

You might try a manual reinstall or update.

I deleted the bad theme and now my blog page is completely blank. There’s nothing on it at all, as if wordpress isn’t even installed .

Just log-in your administration panel and activate another Theme , this “forces” WordPress to reset its status . Read this article
If you have only the default theme , Install another theme from www.remarpro.com , just to have the option to switch themes .