Sometimes the problem is that there is no problem. Trying to debug it more can make the situation even worse - while the real problem was caused by debugging in the first place!
If you have mysterious freezes while debugging UITableView, try reducing the amount of logging. Fixed one such problem by NOT sending any NSLog messages from cellForRowAtIndexPath delegate callback. Seems like too many log messages messed up internal iOS timing.
Wonder how many times I have to re-iLearn this iLesson!