The code I downloaded yesterday only had the fix applied to the addition operator. The following code should fix the subtraction, muliplication and division operators:
// case TypeCode.Decimal: throw new InvalidOperationException("Operator '' can't be applied to operands of types 'double' and 'decimal'");
case TypeCode.Decimal: return (Double)a  Convert.ToDouble(b);
...
// case TypeCode.Double: throw new InvalidOperationException("Operator '' can't be applied to operands of types 'decimal' and 'double'");
case TypeCode.Double: return (Decimal)a  new Decimal((double)b);
// case TypeCode.Decimal: throw new InvalidOperationException("Operator '*' can't be applied to operands of types 'double' and 'decimal'");
case TypeCode.Decimal: return (Double)a * Convert.ToDouble(b);
...
// case TypeCode.Double: throw new InvalidOperationException("Operator '*' can't be applied to operands of types 'decimal' and 'double'");
case TypeCode.Double: return (Decimal)a * new Decimal((double)b);
// case TypeCode.Decimal: throw new InvalidOperationException("Operator '/' can't be applied to operands of types 'double' and 'decimal'");
case TypeCode.Decimal: return (Double)a / Convert.ToDouble(b);
...
// case TypeCode.Double: throw new InvalidOperationException("Operator '/' can't be applied to operands of types 'decimal' and 'double'");
case TypeCode.Double: return (Decimal)a / new Decimal((double)b);
