Permalinks broken for custom post types?

Hi,

My custom post type permalinks are resulting in 404 pages. They were working fine a few days ago as

http://site.com/customposttype/slug

now that results in 404 page. Permalinks are set as /%postname.

However a ?post_type=custom&p=n will find the correct page.

Anyone else notice any changes with this?

Chris.