Hi Dunja,
I still fail to understand what makes you believe this is SSO related. It is related to the system interaction, however as you stated, in one case you log in to a portal and in the other case directly to the SAP system. I would bet, there is something wrong with NLS settings in the two systems. However this is not related to SSO. I would suggest you ask this question in a from related to printing questions.
Regards,
Patrick