403 forbidden when loading /wp-admin/index.php

We’ve had our blog up and running for about a month, with no troubles. I made some updates to it today which added a custom image to the header and sidebar – nothing at all complex. The changes took – but now when I attempt to log into the admin, it gives me a 403 forbidden error, the first time it’s done this. I did a search on the forum for this error, and didn’t find any answers that seemed relevant to my situation. Can anyone help guide me through this? Thanks alot!