failed to start hbase!!

[siyuan.tong]

# start-hbase.sh

SFserver176: Exception in thread "regionserver60020" 
java.lang.NullPointerException
SFserver176:     at 
org.apache.hadoop.hbase.regionserver.HRegionServer.join(HRegionServer.java:1417)
SFserver176:     at 
org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:683)
SFserver176:     at java.lang.Thread.run(Thread.java:662)
Hi all.
What's wrong with NullPointerException when I start the regionserver?