You can disable the plugin by logging in via FTP, and going to wp-content/plugins/ and deleting the secure-login folder.
Could you provide some details on plugin version, WordPress version, and what your current permalink structure is?
I’m not quite sure I understand the problem, but in order to disable a plugin manually, just delete it from the WordPress plugins directory. Log in to your server via FTP, and locate the wp-content/plugins directory. Delete the secure-login directory and WordPress will disable the plugin.
There seems to be a problem with the permalink flushing. For a quick fix, visit the permalinks page under “settings > permalinks” and hit save. That will manually flush the rewrite rules and should fix the problem.
