Installation on Debian – all PHP pages are blank

I have just installed the latest WordPress on Debian Unstable using apt-get.
1. I installed apache2
2. I installed mysql and configured users.
3. I installed php4, configured apache to work with it, configured php.ini – allowed global vars and all errors.
4. Wrote a test script for php – worked fine
So I am pretty sure it is not a web-server configuration issue.
I copied the wordpress directory to my site.
But when I fire up mysite/wp-admin/install.php I get a blank page. The same is for all php pages of wordpress.
Do you have any ideas?
I read all the posts for the last 2 weeks – none like mine.