login isn't working properly

There seems to be something weird going on with the login on my site...

I have a front page on my site with a login block on it. When you login, you're supposed to be brought to the "logged in ".

When I submit my username and password, the page simply re-loads. It does not bring you to the new "logged in . It loads the correct blocks on the left side (ex: my profile, admin, etc), but doesn't re-direct.

Sorry if this explanation isn't very clear ... does anybody have any idea what could be wrong?