WARN ipc.Client: Exception encountered while connecting to the server

While Running hadoop 0.20.S, when I run this command "hadoop dfs -ls" I got this error

WARN ipc.Client: Exception encountered while connecting to the server : javax.security.sasl.SaslException: GSS initiate failed [Caused by GSSException: No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt)]
Bad connection to FS. command aborted. exception: Call to localhost/127.0.0.1:8020 failed on local exception: java.io.IOException: javax.security.sasl.SaslException: GSS initiate failed [Caused by GSSException: No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt)]

after some googling I run this command
kinit username
and enter the password of kinit
eg my username is hadoop-user

so final command is
kinit hadoop-user
now enter password for kinit (note this password is not same as your username password)

java.lang.ClassNotFoundException: WordCount$Map

Today I was trying to run mapreduce wordcount code on my eclipse, I copied code from here http://wiki.apache.org/hadoop/WordCount
but with this I was getting following error,
java.lang.RuntimeException: java.lang.ClassNotFoundException: WordCount$Map

after bit of googling I found
add the commented line below
Job job = new Job(conf, "wordcount");
//job.setJarByClass(WordCount.class);

Now its working :)