.htaccess or AdminCP issue?

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Hi there,
I put a link to my admincp in the navbar, but when I click on it, It says:

/admincp/?username=admincp
This then fills the username field with admincp and keeps password field blank.


I added lines to the .htaccess file to make profile names shorter. This is all that is contained in my .htaccess file:

PHP Code:

RewriteEngine on
RewriteRule ^/?([a-zA-Z0-9]+)$ member.php?username=$1 [L]
RewriteCond %{HTTP_HOST} ^http://www.yoursite\.com 


Nothing else is contained in the file.

Please help me as this is really annoying me