SSL Decryption with Wireshark - Cached Certificate?

That's what I thought too, but had some difficulty. However my methodology must have been incorrect somewhere, because I just tried it again and it worked. I captured an SSL session with tcpdump, configured Wireshark with the private key, and validated unsuccessful decryption with the error I have already noted. Then I changed the Cache Size value in the Client SSL Profile that is applied to the VS from the default (20000) to zero, and did another capture. This time Wireshark was was able to successfully decrypt.