Blank page

Hi!
I have no idea what to do now… I was prepared that after my server NT4 => Debian Linux switch there would be some problems, but this is insane.
I’ve tried for 6 hours now to fix the “blank page” problem that some other people have been experiencing, and that I’ve been experiencing since the switch.
The problem:
Blank page on most WP pages I start (admin login, index.php).
phpinfo.php works, and so do some test-scripts I’ve written to check if database access works.
The “blank page” is a blank HTML site containing only the bare essentials for HTML. No error messages, nowhere…
If I knew PHP I’d take the script apart and check what’s the problem…. it seems like pages get parsed pretty well by my interpreter, but no result is returned.
Details of my system:
Apache/2.0.47 (Debian GNU/Linux) PHP/4.3.4 Server
PHP is a module, loaded, and the mysql extension is loaded and works (check with test script).
Please… I love the WordPress script. But I have no idea left what I could do… I tried reinstalling php and the mysql module a few times, I tried taking stuff out of the PHP scripts to see if it would give me any error, I checked almost any option in php.ini… I don’t get any errors or hints, nothing. Only a blank page.
Thank You for helping… I’d be up for a complete bugfixing session too, to track down the bug.
P.S.: Another thing I’ve noticed is that when I get a blank page, neither access.log nor error.log of the apache seem to be updated… it’s like I never accessed the page.