its hapen to be before so i went onto the blizzard site n they gave this reason so i quoate: If you can only not access ONE realm then you have a temporary IP restriction, usually due to spamming.
Spamming is:
Gambling, repeated requests for a new screen to see what you wish to gamble for
Spells, repeated use of a spell with no cast delay such as AMP DMG or Glacial Spike can get you booted.
Scrolling through skill selection using the mouse wheel.
Shopping, going up and down a wp to refresh the screen in a shop (see gambling)
Spamming, (original) repeated use of words quickly in a game or in chat.
Muleing, repeatedly joining the same game, and leaving.
Game spam: Repeatedly making/joining new games,
The only cure I am afraid is TIME. Usually it clears between 15 mins and 72 hours.
DO NOT try to connect more than ONCE, if you do, you will find the restrction lasts longer and longer!
Addendum: If you are certain YOU did not spam, maybe someone else on your IP DID, as the restriction is by IP it is possible on shared IPs that someone else is responsible for your restriction. end quote.