wysiwyg: Cannot list attachments for pages with a period "." in their name - TRANSPORT_ERROR

Steps to reproduce:

• Create a new page called "My.Page"
• Add an attachment to the page.
• Edit in WYSIWYG
• Type then highlight some text, then click "Link -> Attached File.."
• Choose "All Pages" tab
• Navigate to the My.Page, then click the "+" plus next to Attachments.
• The Error dialog pops up: "Server returned TRANSPORT_ERROR with no error message."
  (And no attachments are listed)

I'm not seeing an error on the server side, although I would think there should be..