I believe that cr_filename_to_mime_type was added in 4.6.1, not 4.6 itself - did you pull the latest static pages from CVS?
The easiest thing to do is to revisit the download page and install 4.6.1 beta 2, which Jeff Davis uploaded to the repository earlier today or late yesterday.
We expect this to become 4.6.1 final on Friday. I just checked and the proc cr_filename_to_mime_type is in 4.6.1 so you shouldn't run into this problem.
