I have a Mac running OSX 10.5.8. I've tried to download the Mac software for Bitcoin from weusecoins.com many times, but each time the installation fails and I get this message: 'You cannot open the application Bitcoin QT becasuse it is not supported on this architecture'.

I've tried downloading from some of the 'mirror' sites too, but with the same result.

Any ideas about solving this problem would be appreciated.