[TYPO3-english] problem with URL masking

[Szymek]

Hello,

I recently took over page based on Typo3 and it has enabled feature
which mask URL like this:

<domain>/index.php?id=12 into <domain>/12.html

The problem is that after a while of my administration of page masking
stopped working :) eg. main page show off correctly but after i try to
open others i get "Page not found error"

In apache log i have errors like this:
[Thu May 14 15:58:12 2009] [error] [client XXX] File does not exist:
/var/www/html/biblioteki.html

My question is what could possbly cause this error ? and where can i
find configuration for masking URL.

I will add that i have two test sites (copies of the prod site) that
work correctly in other dir's. I even try to copy files from them but
didn't helped (i suppose it have to be some config written in
database).  And when i try to access prod site via not masked URL eg.
<domain>/index.php?id=12 , page show off correctly.

Typo version: TYPO3 Ver. 4.2.1

Regards,
Artur