Membership errors when using redirects

Hello,

I have a blog detail page using the page /blog-entry.php
All blogs use custom keywords in the url followed by the blogs num

For example, the original url would be:
/blog-entry.php?healthy-living-4

For SEO benefits I have the following htaccess rewrite:

Options +FollowSymLinks
Options +Indexes
RewriteEngine on
RewriteRule ^blogs/([^\.]+)$ blog-entry.php?id=$1 [NC,L]

this then allows the following url to see the blog:

/blogs/healthy-living-4

This works great and I have seen a significant increase in seo benefits because of this.
However now I would like to use the membership plugin and I am coming up against a small problem. Logs in as expected but when I want to log OUT it doesn't work - I have tried it on the original full url and it works so it's my rewrite that is doing it!

Here is the code for the log out link:

<?php if ($CURRENT_USER): ?>
<li id="logoff_link"><a href='?action=logoff'>Logoff</a></li>
<?php else: ?>
<li id="login_link"><a href="#login_wrapper">Login</a></li>
<?php endif ?>

Any ideas?

Thanks Jono