[Plugin: SimpleLogin] Errors with 2.0.5 upgrade and does not validate

I’m running WP 2.8.1 and today I upgraded from SimpleLogin 2.0.3 to 2.0.5 via the automatic upgrade in the plugin section of the control panel. The first thing I noticed is that my site would no longer validate as XHTML 1.0 Transitional. It appears the issue was with the following stylesheet link not being properly closed:

<!-- SimpleLogin Version 2.0.5 -->
<link rel="stylesheet" type="text/css" href="http://anythingbutperfect.com/wp-content/plugins/simplelogin/simplelogin.css">
<!-- SimpleLogin Version 2.0.5 -->

I found this code in simplelogin.php and attempted to edit it to add the closing slash /. It then completely broke my site and control panel, giving me the following error: “Warning: Cannot modify header information – headers already sent by (output started at /home/mysite/public_html/wp-content/plugins/simplelogin/simplelogin.php:507) in /home/mysite/public_html/wp-content/plugins/simplelogin/includes/wp-login-actions.php on line 34”. At that point I couldn’t even get back into the control panel to deactivate the plugin. I had to log in via FTP and delete the simplelogin folder from my plugins folder. I then reverted back to 2.0.3 and all is okay in the world again. Any ideas how that error can be fixed so the code can validate?

Thanks!