Recently migrated a Joomla 1.5 site to 3.3. Some but not all of my category blog links worked. It resulted in a “404 – Category not found” error. I would get various messages in the url. There would be “www.something.com/Tracks/thepageIwant.html” or “www.something.com/Read Private Message/thepageIwant.html”
I googled and found my answer here.
Basically delete the menu item and make a new one. Worked perfectly for me.
It gets better I found a “rebuild” button in the menu section. I checked the links that were giving me the 404 and they worked.
Hope this helps someone out there.