I am pretty sure, that the bug is consistent on 64 bit devices running 64 bit code. At least that is what I have experienced.
The bug seems to be with sizeWithFont:forWidth:lineBreakMode:, returning a wrong size in 64 bit. I have no idea why. Some comments in the code seems to suggest that the function does not work with multiline text, even if it appears to do so in 32 bit.
Furthermore, the function is deprecated with iOS7.
If you look around line 1085 in CCTexture2D, you should find a line saying
dim = [string sizeWithFont:font
Try to replace it with this, and let me know if it helps
dim = [string boundingRectWithSize:boundingSize