Mapreduce error:Cannot create a record reader

["ablozhou@gmail.com" <ab...@gmail.com>]

hello,
I run a mapreduce job to process data in hbase table. but I encountered
errors below.



2012-09-03 17:55:20,374 INFO org.apache.hadoop.mapred.JobTracker: Removing
task 'attempt_201208311632_0040_r_000001_2'
2012-09-03 17:55:20,624 INFO org.apache.hadoop.mapred.JobTracker: Adding
task (JOB_CLEANUP) 'attempt_201208311632_0040_m_000001_3' to tip
task_201208311632_0040_m_000001, for   tracker
'tracker_h184:localhost.localdomain/127.0.0.1:37361'
2012-09-03 17:55:23,627 INFO org.apache.hadoop.mapred.TaskInProgress: Error
from attempt_201208311632_0040_m_000001_3: java.lang.Throwable: Child Error
    at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:271)
Caused by: java.io.IOException: Task process exit with nonzero status of 1.
    at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:258)

2012-09-03 17:55:26,629 INFO org.apache.hadoop.mapred.TaskInProgress:
TaskInProgress task_201208311632_0040_m_000001 has failed 4 times.
2012-09-03 17:55:26,630 INFO org.apache.hadoop.mapred.JobInProgress:
Aborting job job_201208311632_0040

.....

java.io.IOException: Cannot create a record reader because of a previous
error. Please look at the previous logs lines from the task's full log for
more details.
 at
org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.createRecordReader(TableInputFormatBase.java:112)
 at
org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.<init>(MapTask.java:489)
 at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:731)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:370)
 at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at java.security.AccessController.doPrivileged(Native Method)
 at javax.security.auth.Subject.doAs(Subject.java:415)
at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121)
 at org.apache.hadoop.mapred.Child.main(Child.java:249)

The hadoop computer is 5 PCs each only have about 2G memory.  why will i
meet IOException like this?
thanks

andy