Line of code causes crash in instruments but not in Xcode

BOOL continueLoop;
CGPoint thePoint;   

while(continueLoop != NO)
{
    continueLoop = NO;

    thePoint = [self generateRandomLocation];

    NSMutableArray *blocks = [self getBlocksForX:thePoint.x];

    for(BlueBlock *block in blocks)
    {
        if(block.getBlockLocationY == thePoint.y)
        {
            continueLoop = YES;
        }
    }
    [blocks release];
}

This causes a crash when ran in instruments but not in Xcode. I narrowed the problem down, it happens when this line of code is in a loop... NSMutableArray *blocks = 开发者_如何转开发[self getBlocksForX: thePoint.x]; the method returns a NSMutableArray, I store it in blocks each time the loop is executed then at the end of the loop I release it. What would be causing instruments to crash?

---

since you never alloc, copy, or retain blocks you should not be releasing it.

It may help for errors like this to run the static analyzer.