Not able to add attributes (e.g. first name) to a mail form in PCUI

I am creating a mail form in PCUI. I am not able to add attributes (e.g. first name) to the mail form. However, I am able to add the attributes in SAP GUI. In other words when I click on "Attibute" button enter attribute name on the pop up and click on "Transfer Attribute" button, the empty attribute is inserted into the text.

Kindly note we are using SAP CRM 5.0 Service Pack 8. We have already taken note of Service Note No. 900628 and correction has already been done in this regards. We are still facing the problem of Empty Attribute for the mail form in PCUI.

Regards,

Deepak