Memory leakage Error

I have initialize开发者_StackOverflow中文版d an object like this

PixelInfo *ob=[[PixelInfo alloc]initWithName:clr :t];

within a for loop and release it within that for loop itself like this.

[faceColor addObject:ob];
[ob release];

But after iterating nearly 120 times i am gtting an error like this:

malloc: *** error for object 0x5030400: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug

Help me to solve this problem..