Hi frosticek,
After several re-installation, I finally found the cause of the problem.
When you checked the "Enable friendly URLs" and go to "Show rules", you will notice that there are options where you can change how your URLs will be styled.
This is what I did...
Under "Page URL:", the default setup was {PAGE_SLUG}-p{PAGE_ID} in actual
http://yoursite.com/about-p26If you want to edit it and just leave {PAGE_SLUG} and remove the -p{PAGE_ID} in there, it will show you this
http://yoursite.com/about which is really clean and nice. However, when you do that, the error will visible. You can't visit the parent categories.
My question is why can't we edit those fields and what do you mean by saying that the cause of the error was in htaccess?
Thanks!