I don't have a db/build file on the machine as I am using the php downloaded version. I've tried again but this time installing it on my Mac at home where I know what the mysql user name is. The current error is:
The following problems are preventing me from installing SilverStripe CMS:
# It looks like .htaccess files can't have rewrite rules. I can't visit http://localhost/~barnacle/ss/db/testinstall (it returned '').
The thing is there was no /db/ folder to start with in the downloaded tarball. Is there meant to be one? If so then can you check what you have in this file as it doesn't seem to exist.