please help.. hardware or software problem?

Pardon? there is nothing wrong with the machine. Worry if the machine spontaneously explodes.

 

Kaiwai's post was both rude, uninformative and useless.

Honestly, I don't know. It's most likely a software issue, as I have seen this happen before. Of course the animations shouldn't lag and it should be fixed with the various software updates.

But then again, if it isn't fixed, there's always the troublesome way of finding out if you machine has a problem:

1. Do the animations lag in Tiger as well?
2. Do the animations lag after a reinstall? (you can also check this booting from another hard-drive)

If they do, it's most likely a hardware issue.