Transparent layers on Photoshop CS4 are not transparent???

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I installed Photoshop CS4 a few days ago, but I have a problem, when I add a transparent layer instead of see the white/gray panel that indicates the transparency, the layer is all black. The transparency is still there, but if the layer is black painted I can not work fine. I've searched in the preferences an other places but I can't find how to change this behavior. What could be the problem? Someone knows how to correct this? Before I had CS2 and all works just fine...