I don't know the internal workings of Chyrp (I've heard about it, but never used it), but if your blog works perfectly without clean URL's, then the problem is probably with Apache, not PHP.
So please, drop the link to your phpinfo file! You're giving away detailed information about your configuration, which might help someone break into your system!
Back to more mundane issues....
1) Did you restart Apache after enabling mod_rewrite?
Code:
a2enmod rewrite
/etc/init.d/apache2 restart
2) Is the .htaccess file provided by Chyrp where it's supposed to be? Did you accidentally leave it out while uploading your site? (One common mistake: if you move files around using the "mv" command, .htaccess files are often left out because they're hidden.)
3) Are there any other .htaccess files, either above or below the directory in question, that interfere with your .htaccess file? (Files with a leading dot in their names are normally hidden in Linux, so use "ls -al" to look them up.)
4) Check the AllowOverride settings in your VirtualHost config file.
Hope this helps,