Hi Chris - I think this is happening because the database provider has been changed and I notice the artwork coming in is no longer compatible with the (very small!) WMP template.
I think you'll find that if you replace the artwork yourself through WMP then it will behave as it did previously... You can either locate the album cover online through Google images or if you can access the 'Folder' image that will do... click copy on the image and then right -click the album square in WMP and select 'Paste Album Art'. (Example below) then WMP will create the hidden files you are missing... Hopefully! - Cheers, Ric.
Click on image for full-size view