.htacces causing URL error with xcart...

Hi there...

I am using the following .htaccess with an apache hosted site on windows running PHP5:

#######START OF .htaccess#######
#DirectoryIndex index.php index.html home.html home.php
#DirectoryIndex index.php

RedirectMatch 404 ^.*/\.pgp.*/.*$
RedirectMatch 404 ^.*/sql/.*$
RedirectMatch 404 ^.*/schemes/.*$
RedirectMatch 404 ^.*/skin1_original/.*$
RedirectMatch 404 ^.*/Smarty.*$
RedirectMatch 404 ^.*/upgrade/.*$
RedirectMatch 404 ^.*/shipping/.*$
RedirectMatch 404 ^.*/var/.*$

RedirectMatch 404 ^.*\.(ini|tpl|sql|log|conf|bak|tpl)$

RedirectMatch 404 ^.*/COPYRIGHT.*$
RedirectMatch 404 ^.*/INSTALL.*$
RedirectMatch 404 ^.*/NEW.*$
RedirectMatch 404 ^.*/README.*$
RedirectMatch 404 ^.*/UPGRADE.*$
RedirectMatch 404 ^.*/VERSION.*$
RedirectMatch 404 ^.*/include/version\.php$
RedirectMatch 404 ^.*/config\.php$
RedirectMatch 404 ^.*/top\.inc\.php$
RedirectMatch 404 ^.*/install\.php$

ErrorDocument 401 "<h1>401 - Forbidden: Access is denied.</h1><br /><p><strong>You do not have permission to view this directory or page using the credentials that you supplied.</strong></p>
ErrorDocument 403 "<h1>403 - Forbidden: Access is denied.</h1><br /><p><strong>You do not have permission to view this directory or page using the credentials that you supplied.</strong></p>
ErrorDocument 404 "<h1>404 - Page not found!</h1><br /><p><strong>The page you requested could not be found!</strong></p>

Options +FollowSymLinks -Indexes -Multiviews

RewriteEngine On

RewriteBase /

RewriteCond %{QUERY_STRING} !phpss_xcseo_url=
RewriteCond %{REQUEST_FILENAME} -f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} \.(htm|html|php|php3|php4|php5)$
RewriteRule ^(.+)$ phpss_xcseo.php?phpss_xcseo_url=$1&phpss_uri_exists=true [QSA,L]

RewriteCond %{QUERY_STRING} !phpss_xcseo_url=
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)$ phpss_xcseo.php?phpss_xcseo_url=$1 [QSA,L]
#######END OF .htaccess#######

This is performing exactly how I want it to perform and rewriting my URL for my hosted xcart store....but if a user trys to register for an account on my store....

E.g.
http://www.myurl.com/register.php
They fill out the form and hit Submit...when the form posts to itself...the url it posts to is:
http://www.myurl.com/\register.php
Thus the system cannot find this... If I get rid of the .htaccess file the register works fine...except my other urls screw up. I need this .htaccess file...but what do i need to change so it does not insert "\" into the url on that link above....

Many thanks,...