I have a TMO 8320 with 4.2 OS. I tried downloads from Google but no version of Google Maps worked for me...
I found a link on this page Google Maps Version 2.2.2 Released | BerryReview.com »
and typed in that long url in BB Browser. After reseting Google Maps, I now have the voice. Again, I did not use the default Google Maps download link from m.google.com. I used the link I paste here.
I don't know where I can get version 2.2.3 but I think 2.2.2 is good enough for me.