I just switched to KDE 4.4.5 and am having some trouble with dolphin. All of my machines dual-boot Windows 7 and linux and all of the linux installs have the directory /C: where the windows partition is mounted. I use this convention because all of the browsers have bookmarks to documentation that is installed locally on the C: drive. This worked fine with nautilus, but dolphin mistakes the C: directory as an unrecognized protocol. If I browse to /C: I get the error "The file or folder C: does not exist." and if I try to access anything in the directory such as /C:/Users, dolphin gives me the error "Invalid protocol"

Is there a workaround and/or is this a known bug? I couldn't find anything.
edit: Funny thing is, if I type the file's url manually in the location bar, dolphin does offer me autocomplete suggestions.

Does it work with Konqueror?

Konqueror is doing the same thing.

This is a regression in the file KIO slave it appears. Please file a bug report at bugs.kde.org.