Hi Stelios,
Yes, it seems to me also, as a bad certificate issue.
If memory serves, I run into this message once, where the certificate was valid. Anyway, Websphere v6 is not a supported app server. Have you tried installing on v5.1?
You might want to read this post, too:
matt cockburn, "Fix for LiveCycle Reader Extensions 7.0 install error" #, 6 May 2005 8:22 amIf you are located in Greece, we may be able to help you. You may contact me "ekokkoris at anodos.gr", should you wish.
Regards,
Evangelos