Not sure about the vista problem (must resist smart remark), but the download problem is a real pain, my guess is that they have deliberately corrupted the package.gz file so that you can't download, in an attempt to claw some bandwidth back from the OS2008 release downloads.
Therefore all packages will fail to install as it is unable to verify them.
But as there is no response from maemo, we will just have to guess.

I suppose you could download the packages manually and install them using dpkg or whatever that dodgy debian command is