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I never noticed anything like that with my old iMac G4. In fact, the power cord was the hardest cord to get plugged in on my iMac G4. The USB cables were also very snug to when plugging in.
 
Never noticed anything of the sort. The only thing less than perfect with my iMac is that the screen is tilted to the right about 2º...

reality
 
I had my 1ghz iMac G4 for about a year, and the power cable was snug, maybe you should try and get a new cable.
 
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