I'm getting the same error. I'm running Openfire 3.8.2, JRE 7, IIS 7 on Windows 2008 R2 Server.
I created my own certificate chain for development (a CA and a server certificate signed by it). The certs work correctly in IIS, and I can import them into the keystore, but I cannot import them into Openfire. I get this error:
There was an error one importing private key and signed certificate. Error message: org.bouncycastle.jce.provider.JCERSAPrivateCrtKey cannot be cast to java.security.KeyPair
