Lost the X-Spam-Score-Header along the way

[Henke]

I *somehow* lost the X-Spam-Score-Header on one of my mail servers.
Starting with 4.61.7, I noticed that neither the detailed SpamAssassin 
report nor the Spam-Score header was added.
So I upgraded to 4.62.2 and the detailed report is added again, however 
still no X-Spam-Score-Header.
Is there any way to find out why it's not added ?

The MailScanner.conf contains

SpamScore Number Instead Of Stars = no
Spam Score Character = s
Spam Score = yes
Spam Score Number Format = %d

and it's still working on another box with 4.61.7 with an *almost* 
identical config.

Regards,

Steffan