Images in library return 500 error
I have a community edition website running version 6.1 4300.
I have an image library using the file system which creates a number of thumbnails. The images are used by a dynamic module displaying dogs waiting for adoption. Since shifting the site from pre-production to production (both on same server) the new images uploaded return a 500 error status. I've compared the images added in pre-production to production and the only thing I can see is that the newer images are published by 'User Not Found'. Being community edition there is only ever one user, so this seems odd.
Works - www.dogwatch.co.nz/.../casey_large.tmb-dw-crop.jpg
Doesn't - www.dogwatch.co.nz/.../chloe600px.tmb-dw-crop.jpg
Can anyone shed some light on this, as I have no idea what is going wrong here. Any help would be appreciated :)
My Apologies, this has been resolved. It seems my clients were still using the pre-production version of the site to upload the images :(