Can't log into my site

I set up a new website some time ago on my hosting server. It is a standard wp instillation (www.blahblah.org). There is also a wp.com site which has somehow gotten entwined with this site (wp.blahblah.org/) When I attempt to log into the www. site it tells me “Login Successful – Updating” and in a few moments I see the log in again! No admin option – I cannot get into the back end of this site. BUT I can get into the backend of the wp.blahblah.org/ site with the normal password. AND when I make changes to the wp site they seem to go on the www. site as well! I have tried editing the password in the db file to no avail. It just does not let me into the www. site. I’m confused – Help anyone?