Report builder error

Hi

I have dataset1 generated from this query

select
  *
from
  [RPT_Pvt_WeDh].dbo.ClientRestraint_ReportData
 WHERE
  [region] = @Region
  and [channel] = @Channel
  and [Cust_Prism_Risk_Class_Desc] = @RiskClass
  and [bank_relationship_type] = @Relationship
  and [DaysClassifications] = @Duration
  and [RST_TYPE_CAT] <> 'COMPLIANT'

But when I run it it complains about query execution failed on that dataset1 incorrect syntax near ','  Interesting thing is it works if I switch default parameters to none for the  [channel] parameter which i have set as multivalue.