Exception about DrawItem

[JiOscar]

I need help now: I'm using smartgwt 3.1 DrawItem Canvas drawing.I had a problem, and background prompts exception information: Uncaught JavaScript. Exception [uncaught exception: [Exception ... "Can not modify properties of a WrappedNative" nsresult: "the 0x80570034 (NS_ERROR_XPC_CANT_MODIFY_PROP_ON_WN)" location: "JS frame ::, douban.com./ 127.0.0.1:1863 / flow / sc / modules / ISC_Core.js :: isc__debug__reportJSError :: line 648 "data: no]] in, line 0"

Anyone help?

My .gwt.xml file config:
<inherits name="com.smartgwt.SmartGwtNoScript" />
<inherits name="com.smartgwt.DrawingNoScript" />
<inherits name="com.smartgwt.tools.SmartGwtTools"/>
<inherits name="com.smartclient.theme.enterpriseblue.EnterpriseBlueResources" />
<inherits name="com.smartclient.theme.enterprise.EnterpriseResources"/>
<inherits name="com.smartclient.theme.graphite.GraphiteResources"/>
<inherits name="com.smartclient.theme.simplicity.SimplicityResources"/>

IE8 is OK.The exception appears in FF 7.0.1.