Confirm registration error with some mail provider

Hi everyone, i am writing here because i have got a problem that i can't solve.
I have installed CD on my Jommla 1.5 with that configuration:
- Generate random password: No
- Admin approval: No
- Email confirmation: Yes
Then users compile registration form, check their emails and activate their accounts. Everything work fine, but few days ago i realise that with some provider ( www.virgilio.it , www.alice.it , and others) when user click on the activation link inside the email appear a page that says:

"You are not aothorized to view that page! It's necessary to login."

Making some reserch i discover that in those email there is written an activation link like

but when the browser open that link is become
an underscore appear between the "c" and the "o" in the word "confirmcode".
Making some research i have also discovered that this noise fact doesn't depend on the OS (linux, windows7, windows xp make always the same problem) and doesn't depend also by the browser (Chrome, safari, IE make always the same project)!

Do you know if it is a known bug?
How can i resolve it?

P.S. Sorry for my english!

Can't confirm your issue. Please upgrade to CB 1.4 and confirm if issue still present. We can't account for how each browser will react to the link. Reviewed source and the link sent with the email is formatted correctly.

I made the upgrade to the v1.4 today, but the problem is still present.
I have also found some problems about the compatibility from CB1.4 to Artio JoomSEF, i made a topic about it!

Can't confirm your issue; please disable your 3rd party SEF and test again (using a newly registered user without SEF). Something is rewriting your URLs.