Can you guess where this exception is coming from?

I've deployed a GWT app and have set up an exception reporter so that I get log entries on the server when a client throws an exception. Usually this is very helpful and I've killed a lot of bugs with this information. However, this stack trace has me stumped:

com.allen_sauer.gwt.log.server.ServerLogImplJDK14 log: Uncaught Exception:
com.google.gwt.event.shared.UmbrellaException: One or more exceptions caught, see full set in UmbrellaException#getCauses
at Unknown.EJb(StackTraceCreator.java:147)
at Unknown.SAb(StackTraceCreator.java:387)
at Unknown.eHb(Throwable.java:46)
at Unknown.KXb(com.google.gwt.dev.jjs.ast.JProgram:0)
at Unknown.AM(SimpleEventBus.java:214)
at Unknown.EM(SimpleEventBus.java:103)
at Unknown.bXb(HandlerManager.java:96)
at Unknown.ux(Widget.java:107)
at Unknown.USb(DomEvent.java:116)
at Unknown.xx(UIObject.java:529)
at Unknown.Mx(Widget.java:141)
at Unknown.ixc(DOM.java:1264)
at Unknown.anonymous(DOMImplStandard.java:187)
at Unknown.HIb(Impl.java:214)
at Unknown.anonymous(Impl.java:57)
at .(:0)
at ==================Caused by==================.(:0)
at Unknown.EJb(StackTraceCreator.java:147)
at Unknown.SAb(StackTraceCreator.java:387)
at Unknown.y0c(Throwable.java:46)
at Unknown.KZc(Number.java:192)
at Unknown.Y$c(Float.java:60)
at Unknown.wV(TextBoxBase.java:106)
at Unknown.yTb(ClickEvent.java:53)
at Unknown.AM(SimpleEventBus.java:204)
at Unknown.EM(SimpleEventBus.java:103)
at Unknown.bXb(HandlerManager.java:96)
at Unknown.ux(Widget.java:107)
at Unknown.USb(DomEvent.java:116)
at Unknown.xx(UIObject.java:529)
at Unknown.Mx(Widget.java:141)
at Unknown.ixc(DOM.java:1264)
at Unknown.anonymous(DOMImplStan开发者_开发知识库dard.java:187)
at Unknown.HIb(Impl.java:214)
at Unknown.anonymous(Impl.java:57)

These are all GWT files, except StackTraceCreator, which is part of gwt-log, the program reporting these exceptions to me. I've never seen this exception on a development machine, and I don't have even the beginnings of reproduction steps.

How can I start to track this down?

GWT apps are by default compiled with obfuscation turned on.

So you can either turn obfuscation off, or try to re-symbolize your stack traces, as explained in this issue report of gwt-log: http://code.google.com/p/gwt-log/issues/detail?id=38

This should probably be used best together with these options in your .gwt.xml file (I assume, you already did that):

<set-property name="compiler.emulatedStack" value="true" />
<set-configuration-property name="compiler.emulatedStack.recordLineNumbers"
     value="true"/>
<set-configuration-property name="compiler.emulatedStack.recordFileNames"
     value="true"/>

(see http://code.google.com/p/gwt-log/wiki/GettingStarted)