After release date 2007-10-06, voice files for file and directory names are not working properly.
To clear things up: do you mean the 6th of October daily build? If so please update to the latest of the "current builds" and report back if the problem still persists and describe exactly what happens; "not working properly" isn't very helpful.
There was a discussion about talk clips not working properly I read in the IRC logs
(link to start of the conversation) but I'm not sure if this is what happpens to you. The developer who found it described it as the clip being cut off too early and seems to be working on a solution. I'm not sure about the current status and cannot check easily because I have no talk clips prepared.
P.S. If you want to discuss possible bugs please state the exact revision number of the build you have trouble with, it's displayed at boot or in the "Rockbox Info" screen under the "System" menu. You could also open up the "rockbox-info.txt" inside the ".rockbox" directory on your computer and state what version it reports.