I decided to buy a Gig stick Gigaram and in the first day using i noticed my ibook running hot (that never hapened) and the fans kicked every time. So i did the Apple Hardware test and it detected the RAM problem. (error code: 2MEM/2/4: DIMM1/J7, and at a second time after reinstalling and came up again: 2MEM/104/4

IMM1/J7).
I replaced with a new 1Gb stick and ran Apple Hardware Test again and this time no errors were find.
I decided to post this experience to help if someone is having the same problem..
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Sorry about my english, i'm posting from Brazil.