[spar303]

It was a conflicting plugin after all, however it was a plugin that I needed to keep. My solution was to make the bridge plugin load first so it can define get_avatar(), by putting this code into the bottom of vbbridge.php:

function this_plugin_first() {
    // ensure path to this file is via main wp plugin path
    $wp_path_to_this_file = preg_replace('/(.*)plugins\/(.*)$/', WP_PLUGIN_DIR."/$2", __FILE__);
    $this_plugin = plugin_basename(trim($wp_path_to_this_file));
    $active_plugins = get_option('active_plugins');
    $this_plugin_key = array_search($this_plugin, $active_plugins);
    if ($this_plugin_key) { // if it's 0 it's the first plugin already, no need to continue
        array_splice($active_plugins, $this_plugin_key, 1);
        array_unshift($active_plugins, $this_plugin);
        update_option('active_plugins', $active_plugins);
    }
}
add_action("activated_plugin", "this_plugin_first");

Hope that helps someone.