Registration Number doesn't work

Ok, i 've cut and pasted my registration number, a message pops up saying invalid #.
SO, i type it in and when i get to the 6, my computer beeps and will not let me put the #6 in!!!
Any ideas?
Thank you!

Just a suggestion, get anew registration key and try it.

Cut and paste and ensure there is no trailing space at the end of it.

Also see http://www.avast.com/eng/faq-registration-license.html