I figured out the query that works for me:

Select S1.*

Into AS_Workspace.dbo.StdPmt_InvAmt_SUM_Removed

From FSW_NZ_JDE_Apr05_Sep12_C.dbo.StdPmt as S1

Inner join ( Select VndNbr, InvNbr, Sum(InvAmt) as InvAmt_Sum

From FSW_NZ_JDE_Apr05_Sep12_C.dbo.StdPmt

Group By VndNbr, InvNbr) as S2

ON S1.InvNbr = S2.InvNbr

AND S1.VndNbr = S2.VndNbr

AND S1.InvAmt = S2.InvAmt_Sum