Links to media file can no longer find attachments from media library

Hi, after recently upgrading to 4.3, everything seems to be running fine, except when you click on a link to an attached file from the media library. This is the message you receive:

This is somewhat embarrassing, isn’t it?
It seems we can’t find what you’re looking for.

I have tried uploading the files again and inserting the links again, but did not resolve the issue. Not sure what else to try. I am running the Twenty Twelve theme, which is the current version.

Thanks for any help you can provide.

Heath.