Interesting Problem Code worked in 10.4 but not in 10.5

FROM : Clayton Leitch
DATE : Sun Jun 22 23:26:22 2008

See code below.  Get a error of “EXC_BAD_ACCESS” when I make entries 
in the GUI.  Code used to work with no problems.  It appears that it 
is doing an illegal substraction, which I think means the objects are 
not being initialized with a value of 0.  At least that is my guess.
#import "MonthlyReport.h"


@implementation MonthlyReport
+ (void)initialize
{
   if (self == [MonthlyReport class])
   {
       NSArray *keys = [NSArray arrayWithObjects: @"reportCumActualCost", 
@"reportActualCost", @"reportPredictedCost", 
@"reportCumPredictedCost", @"reportCumlativeInvoiceTotal", 
@"reportMonthlyInvoiceAmount", nil];
       [self setKeys:keys 
triggerChangeNotificationsForDependentKey:@"reportCumDifference"];
       [self setKeys:keys 
triggerChangeNotificationsForDependentKey:@"reportCurrentDifference"];
       [self setKeys:keys 
triggerChangeNotificationsForDependentKey
:@"reportPercentDifferenceMonth"];
       [self setKeys:keys 
triggerChangeNotificationsForDependentKey
:@"reportPercentDifferenceCum"];
       [self setKeys:keys 
triggerChangeNotificationsForDependentKey
:@"reportInvoiceMonthlyDifference"];
       [self setKeys:keys 
triggerChangeNotificationsForDependentKey
:@"reportInvoiceCumlativeDifference"];
   }
}

//Calculate differences
- (NSDecimalNumber *)reportCurrentDifference;
{
   return [[self valueForKey:@"reportActualCost"] 
decimalNumberBySubtracting: [self valueForKey:@"reportPredictedCost"]];
}
- (NSDecimalNumber *)reportCumDifference;
{
   return [[self valueForKey:@"reportCumActualCost"] 
decimalNumberBySubtracting: [self 
valueForKey:@"reportCumPredictedCost"]];
}
- (NSDecimalNumber *)reportInvoiceMonthlyDifference;
{
   return [[self valueForKey:@"reportMonthlyInvoiceAmount"] 
decimalNumberBySubtracting:[self valueForKey:@"reportActualCost"]];
}
- (NSDecimalNumber *)reportInvoiceCumlativeDifference;
{
   return [[self valueForKey:@"reportCumlativeInvoiceTotal"] 
decimalNumberBySubtracting:[self valueForKey:@"reportCumActualCost"]];
}

//Calculate percents
- (NSDecimalNumber *)reportPercentDifferenceMonth;
{
   return [[[self valueForKey:@"reportCurrentDifference"] 
decimalNumberByDividingBy: [self valueForKey:@"reportPredictedCost"]] 
decimalNumberByMultiplyingByPowerOf10: (short)2];
}
- (NSDecimalNumber *)reportPercentDifferenceCum;
{
   return [[[self valueForKey:@"reportCumDifference"] 
decimalNumberByDividingBy: [self 
valueForKey:@"reportCumPredictedCost"]] 
decimalNumberByMultiplyingByPowerOf10: (short)2];
}



@end