unable to find valid certification path to requested target

Hi,

I am working with an SSL server that has a self-signed certificate.
I am getting the following error from SoapUI when I attempt to inspect the WSDL of the server.

Error loading [https://in1-internalrp.agdev.local/cbis/cbis-war-generic-uk-V7-SNAPSHOT/webservices/stp.wsdl]: org.apache.xmlbeans.XmlException: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

I am using

SoapUI v4.6.4 on OS X Mavericks. java version "1.7.0_45"

Here is what I have tried:

-- Attempt 1
I have extracted the server certificate from the server

$ openssl s_client -connect dev-server:443

and installed in to the core keystore for Java

keytool -keystore /Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home/jre/lib/security/cacerts -import -alias dev-server -file dev-server.pem -trustcacerts

and restarted SoapUI (no luck)

-- Attempt 2
Imported the PEM into the Mac Keychain. (restarted SoapUI and tested)
no luck

-- Attempt 3
Created a standalone keystore and specified it's parameters in the SSL Settings in SoapUI Preferences (along with the password)

$ keytool -import -alias dev-server -keystore dev-servers.keystore -file dev-server.pem

no luck.

Does anyone have any suggestions ?
I have read somewhere that SoapUI ignores SSL errors anyway (but that does not seem to be the case).
I have also checked that the server name matches the certificate CN name, which it does.