GWT was having trouble talking to mozilla on linux, producing this ugly error:
** Unable to load Mozilla for hosted mode **
java.lang.UnsatisfiedLinkError: /home/nick/eclipse/plugins/com.google.gwt.eclipse.sdkbundle.linux_1.6.4.v200904062334/gwt-linux-1.6.4/mozilla-1.7.12/libxpcom.so: libstdc++.so.5: cannot open shared object file: No such file or directory
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1778)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1674)
at java.lang.Runtime.load0(Runtime.java:770)
at java.lang.System.load(System.java:1005)
at com.google.gwt.dev.shell.moz.MozillaInstall.load(MozillaInstall.java:190)
at com.google.gwt.dev.BootStrapPlatform.initHostedMode(BootStrapPlatform.java:53)
at com.google.gwt.dev.HostedModeBase.
at com.google.gwt.dev.SwtHostedModeBase.
at com.google.gwt.dev.HostedMode.
at com.google.gwt.dev.HostedMode.main(HostedMode.java:230)
turns out this is a lot less of a problem then I initially thought from scouring forums. Fiddling with permissions on Mozilla files is not needed, just revert your standard C library back to 5 from 6:
sudo apt-get install libstdc++5
Easy peasy, GWT hosted mode back in business on Linux.