effects of scroll view delegate methods on tableview

I am trying play with all the methods on protocol methods of UIScrollViewDelegate on a tableview, things work fine but two issues

1. the scrolling is not smooth, it stubs in between, could be because of large cells (heights are like 80px.
2. Crash, very rarely happens but could not figure out the reason behind the issue

Please help me to find out the reasons for both the issues.thanks.

Date/Time: 2013-07-25 17:20:41.675 -0700 OS Version: iPhone OS 5.1 (9B176) Report Version: 104

Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x00000008 Crashed Thread: 0

Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 libobjc.A.dylib 0x37ed7f78 objc_msgSend + 16 1 UIKit 0x32aa573e -[UIGestureRecognizer setState:] + 206 2 UIKit 0x32af86c4 -[UILongPressGestureRecognizer enoughTimeElapsed:] + 132 3 CoreFoundation 0x3366e1f4 -[NSObject performSelector:withObject:] + 36 4 UIKit
0x32a9f1fe -[UIDelayedAction timerFired:] + 74 5 Foundation
0x37d4f606 NSFireTimer + 138 6 CoreFoundation
0x336e3a2c __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION + 8 7 CoreFoundation 0x336e3692 __CFRunLoopDoTimer + 358 8 CoreFoundation 0x336e2268 __CFRunLoopRun + 1200 9 CoreFoundation 0x3366549e CFRunLoopRunSpecific + 294 10 CoreFoundation
0x33665366 CFRunLoopRunInMode + 98 11 GraphicsServices
0x36a19432 GSEventRunModal + 130 12 UIKit
0x329d2e76 UIApplicationMain + 1074