When I moved this blog from former IIS to this Apache hosting I wanted to enable “pretty” permalink structure /year/month/day/topic, knowing that mod-rewrite was installed and active. But when I did that – every link resulted in 404 “Not Found” error. Trying to find solution I in WordPress support forums or even googling it was to no avail.
Finally I realised that when WordPress was enabling new link structure, for some reason it wasn’t writting rewrite rules into .htacess file. So, I put them there manually:

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . / [L]

And it worked.