We just published a website redesign with upgrade from version 2.3 to 2.6. There is a weird bug. When I click in a link, I may be redirect to a random post or get trapped in a redirect loop. This is mostly to happen in Firefox.
I could see there is a new feature in 2.5 or 2.6 to find old permalinks to a post, and redirect them to avoid 404 error, but I did not found any doc about this feature.
The website: http://idanca.net/
I've tested without all plugins, with Kubrick, everything. This does not happen at the wp-admin. What can it be?