BBcode Greasemonkey Multiline tags

I have a greasemonkey script that replaces BBcode with HTML because the admin of a site I frequent won't implement text effects. The problem is when users use tags with multiple lines in them they don't work.

For example:

[ b ]text text text[ /b ]

Shows as text text text

[ b ]
text
text
text
[ /b ]

Shows as
[ b ]
text
text
text
[ /b ]

Here is the full script. Any ideas on how to make multiple lines work?
http://snipt.org/kkml

**I mainly just want to get the quote tag working, that's the one they use the most and mess up on by adding multiple lines.***

First and only bump. Anyone have any ideas?