The have gone into the new forum, due to the fact Google cache got not updated yet you still get the old links.
Switch to your Forum/Category (see my signature for ITRC Tree links), enter your search in the search box (top right). Enjoy a working search function inside the forum.
More information regarding search and browsing are found here:
I noticed that too, but you can 99% of the time click on the "cached" version and get what you are looking for. Granted you can't reply back to those messages, but at least you can get some of the content.
I believe I saw someone suggest that they thought once google indexes the whole new forums they thought things would be better.