I get the same error, only I don't have brackets in my urls. It just won't let me post any. I write it out manually, and I get the error. I use the link button when writing a post, and it still gives me that error. :s

I'm having the same problem with two different installations of v0.9.2. Users receive an invalid url error when attempting to post href tags with:

* = * _ * & [/list:u]

As a side note for anyone stuck with this problem, my current workaround is simply switching off html_checker in conf/_formatting.php

$use_html_checker = 0;

but as advised, I have switched security_checker on:
$use_security_checker = 1;