Does your proposed address (don't post it) in fact contain any of these forbidden characters, i.e. accented letters or punctuation signs?
If not it sounds like a glitch at the server end: the first thing to do is to give it a day or so and try again. If it still doesn't work you will have to contact Support.
To contact iCloud Support: if you currently happen to have AppleCare, either because you recently bought Apple hardware or have paid to extend the inititial period, you can contact them here:
http://www.apple.com/support/icloud/contact/
You will need the serial number of the covered hardware.
If you are not covered by AppleCare, then - in common with other free email services - there is no free support and you may be asked to pay a fee. You can reasonably insist that as it's their problem you shouldn't be charged.