Cannot switch spam filter

[preluderd]

I changed the default Spam filter component from Plesk SpamAssassin 3.2.3 to Smarter Mail SpamAssassin 5.1.3051 in 'Server > Plesk Control Panel Components Management > Spam Filter' and cannot switch it back to Plesk SpamAssassin 3.2.3. When I try to Plesk just hangs on the "Please wait loading...". None of my email is getting filtered from spam.