I'm reposting this for English speakers - originally posted in the German titled thread.
Version 2.4 is causing comments section to fail.
Yes I am also getting the same error - unable to make comments.
I came here after a process of elimination - turned off all plugins and slowly turned them all back on again, I found it hard to believe that antispam bee was causing the issue - it [was] a great plugin!
So, what to do - I have disabled it for now and will consider downgrading back to v2.3 - but then you always get the upgrade message.
Perhaps the developer has gone quiet because he is busily trying to find the issue :-)