soapUI-3.0 script fails to locate java on 64-bit Ubuntu

When I run soapUI-3.0 on 64-bit Ubuntu 9.04 I get an unsatisfied link error (below). JDK 1.6 Update 14 is installed, the java executable is in the path, and JAVA_HOME is set, but it is trying to use a bundled copy of the JRE. If I explicitly set the JRE location at the top of the soapUI-3.0 script it works, e.g. "INSTALL4J_JAVA_HOME_OVERRIDE=/opt/jdk1.6.0_14".

java.lang.UnsatisfiedLinkError: /home/clint/apps/eviware/soapUI-3.0/jre/lib/i386/xawt/libmawt.so: libXext.so.6: cannot open shared object file: No such file or directory
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(Unknown Source)
at java.lang.ClassLoader.loadLibrary(Unknown Source)
at java.lang.Runtime.load0(Unknown Source)
at java.lang.System.load(Unknown Source)
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(Unknown Source)
at java.lang.ClassLoader.loadLibrary(Unknown Source)
at java.lang.Runtime.loadLibrary0(Unknown Source)
at java.lang.System.loadLibrary(Unknown Source)
at sun.security.action.LoadLibraryAction.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Toolkit.loadLibraries(Unknown Source)
at java.awt.Toolkit.(Unknown Source)
at java.awt.Dimension.(Unknown Source)
at com.eviware.soapui.support.UISupport.(UISupport.java:125)
at com.eviware.soapui.SwingSoapUICore.importSettingsOnStartup(SwingSoapUICore.java:107)
at com.eviware.soapui.SwingSoapUICore.initSettings(SwingSoapUICore.java:89)
at com.eviware.soapui.DefaultSoapUICore.init(DefaultSoapUICore.java:125)
at com.eviware.soapui.StandaloneSoapUICore.(StandaloneSoapUICore.java:35)
at com.eviware.soapui.SoapUI.main(SoapUI.java:618)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.exe4j.runtime.LauncherEngine.launch(Unknown Source)
at com.install4j.runtime.Launcher.main(Unknown Source)