Serialization Exception while upgrading to GWT 2.8.2

I am upgrading to GWT 2.8.2 from GWT 2.6.0 and getting the following error:

com.ptc.cat.ops.client.internal.OperationManager

SEVERE: DefaultOperationManager-> Failure dispatching operation

com.google.gwt.user.client.rpc.IncompatibleRemoteServiceException: The response could not be deserialized

at Unknown.Throwable_1(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.Exception_1(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.RuntimeException_1(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.new IncompatibleRemoteServiceException_1(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.onResponseReceived(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$fireOnResponseReceived(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.onReadyStateChange(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.<anonymous>(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.apply_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.entry0_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.<anonymous>(com.ptc.windchill.wncgwt.WncGWT-0.js)

Caused by: com.google.gwt.user.client.rpc.SerializationException: java.util.LinkedHashSet/1826081506

at Unknown.Throwable_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.Exception_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.new SerializationException_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$check(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$instantiate(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$readObject(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.deserialize_668(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.deserialize_697(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$deserialize_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$deserialize(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$readObject(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.deserialize_337(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.deserialize_335(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$deserialize_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$deserialize(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$readObject(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.read_8(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.onResponseReceived(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.$fireOnResponseReceived(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.onReadyStateChange(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.<anonymous>(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.apply_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.entry0_0(com.ptc.windchill.wncgwt.WncGWT-0.js)

at Unknown.<anonymous>(com.ptc.windchill.wncgwt.WncGWT-0.js)

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