Below is a known issue with 6u37 (not sure if it applies to your issue):
Synopsis: Regression - Issue in parsing jvm args for Java Web Start relaunch on Unix platforms.
Some combinations of java-vm-args and <property> elements in a jnlp file may cause some properties to be set incorrectly when Java Web Start is forced to relaunch. The problem is applicable to Solaris and Linux platforms.
In some cases, adding dummy property elements to the jnlp file may help prevent the problem.