In the same site[http://site.com/index.php], using the same rules[ex:+abcd and
+%28abcd%29], a relative link as:
a href="?open=abcd"
is properly scanned and recorded. But a relative link as:
a href="?open=%28abcd%29" is not recorded.

I tried to change the scan rules to [+(abcd)] instead of [+%28abcd%29], but
still don't get any link with parenthesis. There is a "escape" needed to
parenthesis (or any other special characters) in the scan rules or something
like this? 

The only way to make the scan works was changing the parenthesis to a * in the
scan rules[+*abcd*].

I didn't find anything about special or "reserved characters" or "how to
escape characters" in the manual or faqs, so I'm just reporting.