After installing/activating AWPCP (Another WordPress Classified Plugin), when I type wp-admin/ I get a blank page but with /wp-login.php the login appears.
I this there’s a problem with redirection or .htaccess with that plugin but I can’t find out what it is.
the plugin is causing a 500 error but php debugging is turned off. The fix it, FTP into the server and remove the plugin then your admin will be back up and running.
Looks like (for me) your plugin generate PHP Fatal Error on wp-admin initiatation. And this dosn’t have any relation to redirection. Suggest you to debug it with WP_DEBUG. Enabling it and you will be able to see what errors generated whan you opening wp-admin.
Maybe the wrong mode for copy files of the plugin via FTP? If the WP_DEBUG have no return, then it is this or whitespace on the start or end of the plugin files.