wsdl2objc is not working with iphone SDK 4.2

We had a project using wsdl2objc to generate webclient for iphone application. The app was working fine with SDK 3.2, till lately we tried to test it with the new Xcode (SDK 4.2) and it throws strange EXC_BAD_ACCESS directly after sending an asynchronous request and surely never getting a response. Here is the stack trace:

0   libsystem_c.dylib                 0x3452a200 OSAtomicAdd32 + 0
1   Foundation                        0x30c317a4 -[NSOperation release] + 24
2   CoreFoundation                    0x343df19a CFRelease + 62
3   CoreFoundation                    0x343e1eb4 _CFAutoreleasePoolPop + 140
4   Foundation                        0x30c211c4 -[NSAutoreleasePool release] + 92
5   UIKit                             0x34b70f08 _UIApplicationHandleEvent + 5784
6   GraphicsServices                  0x31884e70 PurpleEventCallback + 660
7   CoreFoundation                    0x34451a90 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 20
8   CoreFoundation                    0x34453838 __CFRunLoopDoSource1 + 160
9   CoreFoundation                    0x34454606 __CFRunLoopRun + 514
10  CoreFoundation                    0x343e4ebc CFRunLoopRunSpecific + 224
11  CoreFoundation                    0x343e4dc4 CFRunLoopRunInMode + 52
12  GraphicsServices                  0x31884418 GSEventRunModal + 108
13  GraphicsServices                  0x318844c4 GSEventRun + 56
14  UIKit                             0x34b9bd62 -[UIApplication _run] + 398
15  UIKit                             0x34b99800 UIApplicationMain + 664
16  FFMobile                          0x00002ed4 0x1000 + 7892
17  FFMobile                          0x00002e88 0x1000 + 7816

I know it has to be something about releasing NSOperation. But I could not go any further. Does anybody know if the NSOperation is changed since SDK 4.0? Did anybody successfully test wsdl2objc with SDK 4.0?

EDIT: The WSDL th开发者_运维技巧at I use is here.