Getting "Page not found" with message 500.shtml when adding node of CCK content type

Hi,

For a website I have, I use /node/add/book-ad to add a node of a content type I created (book_ad).

When I click Save to add the node, I get the "Page not found" for the same path, even though I just used it to try and add the book. The node is not saved and does not appear on the site.

The Drupal log has:

Details
Type page not found
Date Sunday, February 13, 2011 - 16:43
User bbasadmin
Location http://[domain].com/node/add/book-ad
Referrer http://[domain].com/node/add/book-ad
Message 500.shtml
Severity warning
Hostname 69.196.173.249

SOLUTION

The solution was to remove a computed_field. The code in this field is below, where [domain] :

if (!$node->nid) node_save($node);

$var_url = "http://[domain]/user/".$node->uid."/contact";

$node_field[0]['value'] = "<a href="."\"".$var_url."\"".">Click here</a>";

Any help would be much appreciated.