On Windows, nsFileSpec is apparently failing when enumerating a folder (not a volume, but a directory inside of it) if the folder's URL ends with a slash. For example, run apprunner, load in "resource:/res/rdf/sidebar.xul" and open the "File System" folder. All the available drives will be listed. Now, open up "C:". You'll see all the contents of "C:". However, you WON'T be able to open "C:\Program%20Files\". I believe this bug appeared right after a fix went it to append slashes onto the end of file URLs that pointed to directories.

Accepting bug

Fix was checked in 3/19. Marking it so.

Bulk moving to XPCOM, in preparation for removal of XP File Handling component. (XPFH has received two bugs in ~5 months, and is no longer in active use.)