I can reproduce this same limitation in Windows XP. folder #52 and on do not appear in the men, but the layouts contained within them do.
This can be replicated pretty easily with a test file where you open Manage | Layouts and use the duplicate buttons to create 52 or more folders with at least one layout inside each.
Andrew G. Grant:
Thank you for your post.
This problem has been previously reported (not on the forum), and our Development and Testing departments are aware of this issue. At this time, no other information is available.