hi,
are u getting any 'file operation error'?
Check the permissions of the ORACLE_HOME/network/agent
where the managed node is. Verify that the preferred
credentials on the console side has write access to 
the $ORACLE_HOME/network/agent directory. 
Check that you have sufficient disk space at the 
Managed node where the Intelligent Agent is installed.
and for further diagnosis,
pls look into oms.log and post the exact specific error messages