CAS w/ SPNEGO Authentication error - authentication

Question

I'm trying to set up CAS SSO with SPNEGO on a Windows environment. I've followed all the instructions in http://jasig.github.io/cas/4.0.x/installation/SPNEGO-Authentication.html but the authentication process fails.
This is the output from the cas.log:
2015-03-04 11:36:22,732 DEBUG [org.jasig.cas.support.spnego.web.flow.SpnegoNegociateCredentialsAction] - Authorization header not found. Sending WWW-Authenticate header
2015-03-04 11:36:22,738 DEBUG [org.jasig.cas.web.support.CasArgumentExtractor] - Extractor did not generate service.
2015-03-04 11:36:22,738 DEBUG [org.jasig.cas.support.spnego.web.flow.SpnegoCredentialsAction] - SPNEGO Authorization header found with 1800 bytes
2015-03-04 11:36:22,739 DEBUG [org.jasig.cas.support.spnego.web.flow.SpnegoCredentialsAction] - Obtained token: `‚A+ ‚50‚1 $0" *†H‚÷ *†H†÷
+‚7
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This is the output from the tomcat server:
04-Mar-2015 11:34:00.187 SEVERE [http-nio-8443-exec-6] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [cas] in context with path [/cas] threw exception [Handler processing failed; nested exception is java.lang.ExceptionInInitializerError] with root cause
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Byte;
at org.jasig.cas.support.spnego.util.SpnegoConstants.<clinit>(SpnegoConstants.java:52)
at org.jasig.cas.support.spnego.authentication.principal.SpnegoCredential.isTokenNtlm(SpnegoCredential.java:133)
at org.jasig.cas.support.spnego.authentication.principal.SpnegoCredential.<init>(SpnegoCredential.java:79)
at org.jasig.cas.support.spnego.web.flow.SpnegoCredentialsAction.constructCredentialsFromRequest(SpnegoCredentialsAction.java:79)
at org.jasig.cas.web.flow.AbstractNonInteractiveCredentialsAction.doExecute(AbstractNonInteractiveCredentialsAction.java:73)
at org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:188)
at org.springframework.webflow.execution.ActionExecutor.execute(ActionExecutor.java:51)
04-Mar-2015 10:41:58.240 SEVERE [http-nio-8443-exec-5] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [cas] in context with path [/cas] threw exception [Handler processing failed; nested exception is java.lang.NoClassDefFoundError: Could not initialize class org.jasig.cas.support.spnego.util.SpnegoConstants] with root cause
java.lang.NoClassDefFoundError: Could not initialize class org.jasig.cas.support.spnego.util.SpnegoConstants
at org.jasig.cas.support.spnego.authentication.principal.SpnegoCredential.isTokenNtlm(SpnegoCredential.java:133)
at org.jasig.cas.support.spnego.authentication.principal.SpnegoCredential.<init>(SpnegoCredential.java:79)
at org.jasig.cas.support.spnego.web.flow.SpnegoCredentialsAction.constructCredentialsFromRequest(SpnegoCredentialsAction.java:79)
at org.jasig.cas.web.flow.AbstractNonInteractiveCredentialsAction.doExecute(AbstractNonInteractiveCredentialsAction.java:73)
at org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:188)
I'm guessing that SPNEGO authentication is failing at Step 5 (Negotiate w/ SPNEGO Token). Does anyone know how to troubleshoot this? Thanks!