Duplicate title and description after permalink edit on wordpress

[specter]

Hello,

I changed almost all permalinks on my wordpress
blog;
Google actually finds both, the old url and the new one; obviously the old is redirected to the new one, correctly, BUT, this seems to result in a title and descritpion tag duplication issue according to Google webmaster's tool reports.
If I type something like www.mydomain.com/new-url all goes well, if I type www.mydomain.com/old-url it regularly redirects on the new one, but for google it still exists.
Does this represent a temporary issue or should I fix it in order to avoid penalties?
Why Google still considers the old url as a real page?

tnx

[tedster]

It's temporary. As long as your server actually returns a 301 status for the url, it will eventually go away.