invisible signature in pdf with itextsharp

Question

hi,

I use itextsharp to sign a pdf document. this works just fine with my certificate. I can see the signature if I open the pdf.

now I install the certificate (double click in windows xp). windows does some stuff and adds it somehow to the system.

now I sign a pdf again and I can't see the signature any more! It looks like the document isn't signed. but if I open this document on another computer I can see the signture again.

Why can I see the signature only on computers where the certificate isn't installed? Funny huh!?

bye bembi