WordPress Hangs when logging in

hi guys, i have a fair few blogs using wordpress software, but one is experiencing a bit of a problem.

When i log in, give username password etc… the page just hangs and doesnt load, the title says dashboard at the top so it knows where it should be going but i dont see anything on the screen

at first it was doing the same on 2.6 i went through the upgrade procedure to 2.7 and still get the same problem.

However the front end of the blog still works!