If you check the url's of "go to first new post" and "View first unread" , you can notice that in the first url the number of the page (i.e #page48) is missing and the syntax of the url is different.
First new post
Code:
http://forum.juventuz.com/showthread.php?32208-Serie-A-Palermo-Juventus-(02-02-2011)&p=2878582
First unread
Code:
http://forum.juventuz.com/showthread.php?32208-Serie-A-Palermo-Juventus-(02-02-2011)/page48#post2878546
First one goes directly to the post number, and the second, that works, includes the page number as well.