URI "file:./" is not hierarchical
The application was so simple and ran locally on tomcat-6.0.16 - it had to be something environmental. Comparing the differences between machines showed that it was the JVM that was different.
The JVM that produced the error was:
java version "1.5.0"
gij (GNU libgcj) version 4.2.4 (Ubuntu 4.2.4-1ubuntu3)
while the Sun JRE 1.6 was okay:
java version "1.6.0_03"
Java(TM) SE Runtime Environment (build 1.6.0_03-b05)
Java HotSpot(TM) Client VM (build 1.6.0_03-b05, mixed mode)
Note that this occurred on Ubuntu 8.04 64 bit Linux:
Linux dev 2.6.24-21-generic #1 SMP Mon Aug 25 16:57:51 UTC 2008 x86_64 GNU/Linux