Two months ago I can't create a new account HOTMAIL, always gives error code 100, but when I put the link directly, without connecting the mikrotik, I can create. What's happening? The problem is only in mikrotik. Displays always this message:

We are working to fix a temporary problem in our subscription service.
Try again.
Error code: 100
OK
Error Code: 100: (0x800482d4 ::):: Thu, 22 May 2008 14:12:03 UTC.

what is the problem?

Sounds like an MTU problem. Search the forums here for Hotmail and MTU. There is a lot of discussion on it with possible solutions.