XLST Transformations Issue in 8.2

Hi All,
We are having issue while XLST transformations for some of the XSLT files. These files were working in Webmethods 7.1.2 but in Webmethods 8.2 throwing following errors. Please suggest. Thanks in advance

Exception Details:

2012-07-06T19:25:16.95Z 2012-07-06T19:25:16.804Z com.wm.pkg.xslt.util.LocalizedTransformerException: [XSL.0002.9002] JAXP: Error during transformation - org.apache.xpath.objects.XString cannot be cast to org.apache.xpath.objects.XNodeSet; SystemID: file:///opt/softwareag/IntegrationServer/packages/BritishPetroleum_Services/pub/xslt/BP_INV_PDF.xsl; Line#: 447; Column#: 84

com.wm.app.b2b.server.ServiceException: com.wm.pkg.xslt.util.LocalizedTransformerException: [XSL.0002.9002] JAXP: Error during transformation - org.apache.xpath.objects.XString cannot be cast to org.apache.xpath.objects.XNodeSet; SystemID: file:///opt/softwareag/IntegrationServer/packages/BritishPetroleum_Services/pub/xslt/BP_INV_PDF.xsl; Line#: 447; Column#: 84
at pub.xslt.Transformations.transformSerialXML(Transformations.java:224)
at sun.reflect.GeneratedMethodAccessor95.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.wm.app.b2b.server.JavaService.baseInvoke(JavaService.java:439)
at com.wm.app.b2b.server.invoke.InvokeManager.process(InvokeManager.java:643)
at com.wm.app.b2b.server.util.tspace.ReservationProcessor.process(ReservationProcessor.java:46)
at com.wm.app.b2b.server.invoke.StatisticsProcessor.process(StatisticsProcessor.java:44)
at com.wm.app.b2b.server.invoke.ServiceCompletionImpl.process(ServiceCompletionImpl.java:243)
at com.wm.app.b2b.server.invoke.ValidateProcessor.process(ValidateProcessor.java:51)
at com.wm.app.b2b.server.invoke.PipelineProcessor.process(PipelineProcessor.java:171)
at com.wm.app.b2b.server.ACLManager.process(ACLManager.java:276)
at com.wm.app.b2b.server.invoke.DispatchProcessor.process(DispatchProcessor.java:30)
at com.wm.app.b2b.server.AuditLogManager.process(AuditLogManager.java:363)
at com.wm.app.b2b.server.invoke.InvokeManager.invoke(InvokeManager.java:547)
at com.wm.app.b2b.server.invoke.InvokeManager.invoke(InvokeManager.java:386)
at com.wm.app.b2b.server.ServiceManager.invoke(ServiceManager.java:234)
at com.wm.app.b2b.server.BaseService.invoke(BaseService.java:194)
at com.wm.lang.flow.FlowInvoke.invoke(FlowInvoke.java:324)
at com.wm.lang.flow.FlowState.invokeNode(FlowState.java:584)
at com.wm.lang.flow.FlowState.step(FlowState.java:444)
at com.wm.lang.flow.FlowState.i…pub.xslt.Transformations:transformSerialXML

Please find the attached sample xsl file.
BP_INV_PDF.xsl (102 KB)