Why do I get a blank page when I create a new node? It seems there are some problems with the content submission. When I select filtered HTML or full HTML, it shows a blank page after submitting a new node. I turned on the error messages, but I still get a blank page with no error message. When the input format is plain text, all works fine.

How do I resolve this issue?
The White Screen of Death (or WSOD) can be caused by a lot of different things.  There is an article about them http://drupal.org/node/158043

Without more information, especially error messages or logs, all answers will be guesses.

Follow the steps in the article above, in order and one by one, to track down your problem.  The first step is making sure you can see errors by adding:

error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);


to you index.php or settings.php.  Once you do this, you should see what is happening and be able to address it.

That said, the two biggest culprits of WSOD are errors in custom code and hitting the PHP memory limit.