copying of attachments not working

Dear all,

Since I've installed Snow Leopard, it seems that copying of attachments from one email into another (select the attachment, press copy, then paste into the body of another email) is not working anymore. Every time I do this the attachment turns into a blue cubicle with a question mark inside it (instead of the thumbnail corresponding with the attachment type).
Now I have to first save the attachment on my desktop, then go into the new mail and select "add attachment" and then add the file.

Does anyone know how to solve this?

Thanks and regards,
Tim Metz