I searched the forum and bug database for this particular issue but I didn't find anything. jboss-seam-excel-2.1.0.GA is referencing a class(org.jboss.seam.excel.ui.UIExcelExport) in the its faces-config.xml that doesn't exist. This causes a ClassNotFoundException on application startup.
Hope this is enough information. I tried to put the stack trace and a copy of the faces-config.xml but the Seam Users Forum post form throws all kinds of errors when I try to do that.