I've logged in several times today, no problems.
Try a tracert, maybe theres a router in the middle somewhere having probs, if thats the case use a cgi proxy to login from a decent hop.
I have however had problems with their new UI, My browser's locked up several times if i leave it open displaying my domains while I'm multitasking. As soon as i return to that window it locks up and have to reboot. Yesterday I went through the tedious task of retrieving multiple EPP Cpodes and submitting each domain to transfer out one at a time, when my browsers crashed i had to start over.