Problem with user details being overwritten

[squishi]

A test site would be a lot of work (because my site is quite big).
Logging is probably the better way. I could log all edits of user info, avatars and profile pics. :erm:

The most annoying thing is that it has not happened again.
Maybe it was just once? Could this happen when I install a plugin but not turn the board off?

I do this in a custom plugin at the "profile_start" hook:

PHP Code:

if ($_REQUEST['do'] == 'nameofplugin')
{
// init user data manager
$userdata =& datamanager_init('User', $vbulletin, ERRTYPE_STANDARD);
$userdata->set_existing($vbulletin->userinfo);
// set custom profile fields
$userdata->set_userfields($vbulletin->GPC['userfield']);
// save the data
$userdata->save();

//...
} 


That should be the right way to do it, no? That's the only place I can think of that could cause this.
Or maybe the bug is that the above code is executed, and then the script saves the data again (in the original code).