Node Save and Forms

Hi All,

On page load I have some code which changes the value of a field of a node. It then calls node_save to save the change to the database. But, that node page also requires a form to be presented to users and it seems as though node_save (or for that matter field_attach_update) somehow disables the form's ability to submit afterwards. Am I missing something here? Is there a specific approach to alter a field value, save it to the database (these two steps are hidden from the user), and then allow the user to submit a form on the node page?

This is my last bug for Version 1 of my site so any help would be greatly, greatly appreciated.

Thanks!