I am using the EWA setParametersAsync call in SharePoint 2010 to set filter values on a PowerPivot slicer. Everything works as long as the passed slicer value is entirely alphanumeric. But if I try a value with a space or some punctuation ("-","/", etc.), the call fails with the error "An error occurred while attempting to set one or more of the parameters in this workbook".
I can't find any indication that parameters or slicer values have any such restriction. Has anyone else come across this?