Oooh.

A) It matters because you shouldn't be able to change the original stopwatch by changing its serialized representation which is supposed to be an independent copy.
B) 'modifying serialized object' ?
C) Make an actual copy of the array instead of just pointing to it.

Can I tell you something?  Something inside me tingled when I set laps = laps last night.  But it was midnight and I went to bed. I'm glad I had at least an inkling!

Unless I am off base of course! =P