Can one of you with the low space error try flashing this hotfix from HTC? It resolves the messaging / email / voice mail errors, but I did a factory reset on my wifes phone before the hotfix file, so Im not sure if it works for low space too.
http://dl3.htc.com/misc/inc8049.apk
Mirror
Make sure you have allowed "Unknown sources" Form the home screen, menu > settings > applications > check unknown sources.
Download the file and transfer to your sd card.
Using a file manager (astro file manager is free and works well), install the file.
Open the app.
Let me know if this worked!