Hi!
if you're using the dev mode constant, you shouldn't even be getting a "Connect to WordPress.com" button, so I'm a little uncertain as to what it going on here, to be honest. Where in the wp-config.php file did you put the line? Did you put it before the
/* That's all, stop editing! Happy blogging. */
?
If you want, you can post your wp-config.php files on pastebin.com so I can take a look (be sure to remove any passwords or other identifying info first, though!)