Ambiguous match found exception when loading statefulfield

Ambiguous match found.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Reflection.AmbiguousMatchException: Ambiguous match found.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[AmbiguousMatchException: Ambiguous match found.]
System.RuntimeType.GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers) +185
System.Type.GetProperty(String name) +26
NHibernate.Burrow.Util.EntityLoader.GetId(Object o) +43
NHibernate.Burrow.WebUtil.Impl.EntityVSFInterceptorBase.OnSave(Object toSave, Object objectInStateContainer) +38
NHibernate.Burrow.WebUtil.Impl.StatefulFieldSaver.ProcessFields() +150
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +47
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldProcessor.Process() +162
NHibernate.Burrow.WebUtil.Impl.StatefulFieldPageModule.page_PreRenderComplete(Object sender, EventArgs e) +60
System.EventHandler.Invoke(Object sender, EventArgs e) +0
System.Web.UI.Page.OnPreRenderComplete(EventArgs e) +2058052
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1566