I'm documenting things here because I've done lots of searching this afternoon trying to find out whats going on and others may also have the same issue wondering why they are getting the following error and it may help someone else who googles it.
SMF LOG ERROR
8: Array to string conversion
File: /home/server/public_html/forum/Sources/Subs.php
Line: 2382
the problem is with this part of the code inserted by youtube bbcode
// Don't parse the content, just skip it.
elseif ($tag['type'] == 'unparsed_content')
{
$pos2 = stripos($message, '[/' . substr($message, $pos + 1, strlen($tag['tag'])) . ']', $pos1);
if ($pos2 === false)
continue;
$data = substr($message, $pos1, $pos2 - $pos1);
if (!empty($tag['block_level']) && substr($data, 0, 6) == '<br />')
$data = substr($data, 6);
if (isset($tag['validate']))
$tag['validate']($tag, $data, $disabled);
$code = strtr($tag['content'], array('$1' => $data)); // <------------------------- HERE!!!!!!!!!!
$message = substr($message, 0, $pos) . "\n" . $code . "\n" . substr($message, $pos2 + 3 + strlen($tag['tag']));
$pos += strlen($code) - 1 + 2;
$last_pos = $pos + 1;
[code]