Ajax search keeps disabling PS 1.3

[damnated]

Hello, I have an older shop set up with PS 1.3.1 and I can't get the ajax search working. I have reindexed and rebuilt the product index, but that isn't the problem.

 

At the Search settings tab in the BO if Enable ajax search, and reload the front page, then check the BO page again, it is set to disabled.

 

I even tried setting the PS_SEARCH_AJAX variable to 1 in ps_configuration table manually in phpmyadmin, but if I reload the front page, and check the table again, it is 0 again.

 

How can I fix this? Please advise!

 

PS: also, it goes without saying, that the real time ajax search doesn't work.