ok so I paid the iPhone repair mecca of Manila, Philippines, a visit a couple of days ago to have phone my looked at since it was in that same place I had my board replaced. The geniuses had this idea that it could be a camera problem or a dusty motherboard that needed cleaning. So they cleaned it and brushed it and replaced my camera with one that they got from another customer's iPhone 3gs that was also being repaired (thieves. I feel bad for the owner of the phone) in the same shop.
The first two days the phone was working great until the same symptoms started showing up again. I demanded, after having paid a kind of hefty price to have the board replaced, that it could (might) be a board problem and have the board replaced again, this time with a decent performing one. They said that they're looking into the problem and are exploring possible solutions to once and for all end my dillemma.
Has anybody else experienced this with their phones? I find it hard to believe that of all the posters here, only I am experiencing this problem.