Normally the message indicates either a connectivity failure (e.g. network issues, database is rejecting traffic, etc.) between the machine where JBoss is running and the database server OR a problem with the connection URL.
The exception is raised by the Oracle driver. You may also want to engage your DBA, network administrators and/or contact Oracle Support directly. It is possible that the database server is sometimes rejecting traffic or else that something is sporadically failing in the network.
1#It seems like there is firewall/network issues in your set up.
2#Check that the database is up and running and accessible from the client machine
3#The exception could be caused by a protocol error, network error, bug in the driver, back-end RDBMS error, etc.
4#This is not a JBoss issue, but should be investigated by:
a. network administrators
b. back-end server administrators (in this case Oracle admins)