Upgrade script won't work

I have 2.7 installed on my vps (installed using the vinstall utility)and have decided to upgrade to 3.0.2 on one site as I want to some functionality of this later version.
I haven’t actually done anything with the wordpress site yet anyway but decided it was better to install 2.7 across all my virtual hosts and then upgrade – simply because that is the standard version installed through software supplied by the hosting company.
I have copied all the files across as described in literature but when I come to run the upgrade script it just hangs – no error message or anything. I have set permissions on the files to 777 to see if it helps but it makes no difference… any ideas.