I answer myself.
Don't know why, but having both jdk 1.5 and jdk 6 installed was the cause of the problem.
Although i was selecting to use jdk 1.5 both using update-java-alternatives and by editing the JAVA_home variable, the only way to fix this was to uninstall jdk 6, and suddenly all went smooth.
[Message sent by forum member 'sep' (sep)]
http://forums.java.net/jive/thread.jspa?messageID=228494