Hmm, do you have the allow images option turned on in config.inc.php?
What version of PHP is installed on the server?
As for slowdowns, a few things you can change to help on this part. Threaded mode is much more server intensive than flat mode and I notice you have the default set to threaded. So, you might want to change the default to Flat. Also, you might want to change the default aged threads to display to a lower number instead of all dates so it doesn't have to pull so many threads from the database.
