[kh99]

Hmm...I don't know why that isn't working. Maybe you can also display the username to see if that's valid. Also you probably need to use $vbulletin->db->escape_string() on the username in case it contains special characters (although it seems unlikely that that's the problem here).

I think you might be able to do this without a query. I guess lastpostinfo is built instead of getting it directly from $forum because categories want to be able to display the latest info from a child? But all the poster info including the userid is already in the $vbulletin->forumcache[] array, so if you searched that array (or the current forum and it's children) for $vbulletin->forumcache[X]['lastposter'] == $lastpostinfo[lastposter], then you could just use $vbulletin->forumcache[X]['lastposterid'].

But I guess that doesn't necessarily fix the problem you're having.