Solver Does Not Function

At work, we have a spreadsheet that uses SOLVER.XLA in a macro. It works fine in Excel '97 but in Excel 2003 it simply does nothing. The code is

s = Application.LibraryPath & "solversolver.XLA"
On Error Resume Next
Workbooks.Open filename:=s
Application.ExecuteExcel4Macro String:="SOLVER.XLA!SOLVER.RESET()"
Application.ExecuteExcel4Macro String:="SOLVER.XLA!SOLVER.OK( PLOT!R46C4,2,0,(PLOT!R13C12:R14C12))"
Application.ExecuteExcel4Macro String:="SOLVER.XLA!SOLVER.OPTIONS(100,100,0.000001,FALSE,FALSE,2,1,1,0.05,TRUE)"
Application.ExecuteExcel4Macro String:="SOLVER.XLA!SOLVER.OK(PLOT!R46C4,2,0,(PLOT!R13C12:R14C12))"
Application.ExecuteExcel4Macro String:="SOLVER.XLA!SOLVER.SOLVE()"
ActiveSheet. Protect DrawingObjects:=False, Contents:=True, Scenarios _
:=True, password:="sigma"

It gives no error message, it simply does not do the calculations. (I took out the error handling line to make sure that there really were no errors being generated!)