cvs checkout gives 'Can't connect to window server - not enough permissions'

Since upgrading from 3.1 to 4.5.3 I am unable to checkout a CVS project. Whenever I do I get the stacktrace (attached)
which ends with 'Can't connect to window server - not enough permissions' .
The problem seems to be related to awt and therefore I have tried setting the -Djava.awt.headless=true system property
in the buildagent's buildAgent.properties (attached) file and in  catalina.sh and in agent.sh
( in both I added JAVA_OPTS="-Djava.awt.headless=true") - but with no success.

Thanks for looking,

Neil