Try something along the lines of this - it ought to work:
function *_activate()
{
global $db;
/*
* Add a new profile field
*/
$profilefield = array(
"fid" => "",
"name" => "MYPROFILEFIELD",
"description" => "MYPROFILEFIELD DESCRIPTION",
"type" => "text",
"maxlength" => "50",
"editable" => "1",
"hidden" => "1",
);
$db->insert_query("profilefields", $profilefield);
$pfid = $db->insert_id();
$db->query("ALTER TABLE ".TABLE_PREFIX."userfields ADD `fid{$pfid}` TEXT");
}
function *_deactivate()
{
global $db;
/*
* Remove profile field
*/
$pfid = $db->fetch_field($db->simple_select('profilefields', 'fid', 'name=\'MYPROFILEFIELD\''), 'fid');
$db->delete_query('profilefields', 'name=\'MYPROFILEFIELD\'');
$db->query('ALTER TABLE '.TABLE_PREFIX.'userfields DROP COLUMN fid'.$pfid';');
}
If you PM me your whole code, I'll take a quick look - it'd be easier that way
