Classic Dev Mode Debugger Broken in IE9 in Latest 5.1d Builds

The classic dev mode debugger seems to have stopped working in the more recent builds of 5.1d. It was working with prior builds of 5.1d from 3/29 and earlier. It fails at app start up time with the following exception below. The line of java code that triggers it is this:

schemaSet.getSchema(dsName);

We rely heavily on the classic dev more debugger as our main tool for debugging our app, since we have not made the switch yet to the Super Dev Mode debugger. So my question is: Is it broken due to a bug in the build, or is this due to support being dropped for this mode?

com.smartgwt.client.core.JsObject$SGWT_WARN: 13:23:46.051:TMR7:WARN:Log:Error:
'Exception thrown and not caught'
in http://localhost:8080/BAAWebApp/com.baa.AccountView/sc/modules/ISC_Core.js
at line 266

crashed in: [c]Class.fireCallback()

Use any version of Internet Explorer other than IE9 for best diagnostics, otherwise Firefox or Chrome
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:105)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
at java.lang.Thread.run(Thread.java:619)


SmartClient Version: SNAPSHOT_v10.1d_2015-04-22/LGPL Development Only (built 2015-04-22)