Ok, to pinpoint the source of this bug I'll need to ask you a bunch of questions to narrow down the possibilities :
Have you been able to log in succesfully to ultima at least once?
Do you have the problem with one account or with several? (if you've only tried one, try making a new account)
Does the screen blink 3 times before it gets stuck or not?
Can you also post the results of speedtest.nl?
Is it possible for you to use another network to test to connect to the game?
Do you have problems with other online games?
I know these are quite some things to check, but the more info you give us, the more we can help you out.