"Could not generate DH key pair" error

I keep getting the following errors, causing outbound secure S2S connections to fail and falling back to unencrypted. How do I solve this?

(I have a generated dh-2048.pem for my associated web server, but OF probably doesn’t know about it – how would I indicate the DH params to OF?)

2014.02.06 13:08:53 org.jivesoftware.openfire.session.LocalOutgoingServerSession - Error creating secured outgoing session to remote server: example.com(DNS lookup: example.com:5269)
java.lang.RuntimeException: Could not generate DH keypair
at sun.security.ssl.Handshaker.checkThrown(Unknown Source)
at sun.security.ssl.SSLEngineImpl.checkTaskThrown(Unknown Source)
at sun.security.ssl.SSLEngineImpl.readNetRecord(Unknown Source)
at sun.security.ssl.SSLEngineImpl.unwrap(Unknown Source)
at javax.net.ssl.SSLEngine.unwrap(Unknown Source)
at org.jivesoftware.openfire.net.TLSStreamHandler.doHandshake(TLSStreamHandler.jav a:222)
at org.jivesoftware.openfire.net.TLSStreamHandler.start(TLSStreamHandler.java:168)
at org.jivesoftware.openfire.net.SocketConnection.startTLS(SocketConnection.java:1 82)
at org.jivesoftware.openfire.session.LocalOutgoingServerSession.secureAndAuthentic ate(LocalOutgoingServerSession.java:433)
at org.jivesoftware.openfire.session.LocalOutgoingServerSession.createOutgoingSess ion(LocalOutgoingServerSession.java:346)
at org.jivesoftware.openfire.session.LocalOutgoingServerSession.authenticateDomain (LocalOutgoingServerSession.java:167)
at org.jivesoftware.openfire.server.OutgoingSessionPromise$PacketsProcessor.sendPa cket(OutgoingSessionPromise.java:261)
at org.jivesoftware.openfire.server.OutgoingSessionPromise$PacketsProcessor.run(Ou tgoingSessionPromise.java:238)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Caused by: java.lang.RuntimeException: Could not generate DH keypair
at sun.security.ssl.DHCrypt.(Unknown Source)
at sun.security.ssl.ClientHandshaker.serverKeyExchange(Unknown Source)
at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
at sun.security.ssl.Handshaker.processLoop(Unknown Source)
at sun.security.ssl.Handshaker$1.run(Unknown Source)
at sun.security.ssl.Handshaker$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.security.ssl.Handshaker$DelegatedTask.run(Unknown Source)
at org.jivesoftware.openfire.net.TLSStreamHandler.doTasks(TLSStreamHandler.java:32 5)
at org.jivesoftware.openfire.net.TLSStreamHandler.doHandshake(TLSStreamHandler.jav a:235)
… 10 more
Caused by: java.security.InvalidAlgorithmParameterException: Prime size must be multiple of 64, and can only range from 512 to 1024 (inclusive)
at com.sun.crypto.provider.DHKeyPairGenerator.initialize(DHKeyPairGenerator.java:1 20)
at java.security.KeyPairGenerator$Delegate.initialize(Unknown Source)
… 20 more