1) clear your temp internet files/cache
2) install the latest version of the flash player just to be safe
3) test
fps to see if you can log in there, if not then its likely your computer. If you can log in then its a legends issue.
4) attempt to log in from a different computer - if you cannot log in from elsewhere, chances are its something to do with the way you're logging in...i don't know how that would be unless you are trying something shady
If you cannot log in from, lets say your school or something, then its weird.
If you cannot log in from home still, that is directly without trying to hide your internet connection.....you know what i mean if you do - that interrupts things....