I was just trying an upgrade,which doesn't have impact on the applications (ahum) and suprise... I bumped on the following nice error when starting the Weblogic node manager:

weblogic.nodemanager.server.NMServer main
SEVERE: Fatal error in node manager server
java.security.ProviderException: setSeed() failed
        at sun.security.provider.NativePRNG$RandomIO.implSetSeed(NativePRNG.java:232)
        at sun.security.provider.NativePRNG$RandomIO.access$100(NativePRNG.java:108)
        at sun.security.provider.NativePRNG.engineSetSeed(NativePRNG.java:92)
        at java.security.SecureRandom.setSeed(SecureRandom.java:393)
        at com.bea.security.utils.random.AbstractRandomData.ensureInittedAndSeeded(AbstractRandomData.java:84)
        at com.bea.security.utils.random.AbstractRandomData.getRandomBytes(AbstractRandomData.java:97)
        at com.bea.security.utils.random.AbstractRandomData.getRandomBytes(AbstractRandomData.java:92)
        at weblogic.security.Salt.getRandomBytes(Salt.java:18)
        at weblogic.nodemanager.server.Encryptor.createProperties(Encryptor.java:116)
        at weblogic.nodemanager.server.Encryptor.<init>(Encryptor.java:85)
        at weblogic.nodemanager.server.NMServer.init(NMServer.java:184)
        at weblogic.nodemanager.server.NMServer.<init>(NMServer.java:147)
        at weblogic.nodemanager.server.NMServer.main(NMServer.java:353)
        at weblogic.NodeManager.main(NodeManager.java:31)
Caused by: java.io.IOException: No such device (errno:19)
        at java.io.FileOutputStream.writeBytes(Native Method)
        at java.io.FileOutputStream.write(FileOutputStream.java:247)
        at sun.security.provider.NativePRNG$RandomIO.implSetSeed(NativePRNG.java:230)
        ... 13 more

Joy joy.. after some investigation I found that this can be solved by adding the following option to the Java command line:

-Djava.security.egd=/dev/random

Then it 'should' work.