Inverting Colour Help

[Nutter]

I'm having problems with inverting colours. (Ctrl + I)

My problem is that when I invert from Black to white, I end up with this colour:


However when I invert from White to Black, there is no problem. It only seems that any colours that are dark won't invert properly.
Now, I definitely know that my black is True Black because I regularly use the "D" key to bring the Default colours back into play, so I know that I haven't accidentally selected a Grey colour.

This is a bit annoying because if I use any blending modes (Multiply, Linear Dodge, etc.), they don't work efficiently.

I am currently using CS2 and any help would be greatly appreciated.

Thanks,
Nutter
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Edit:
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I found out what the problem was after checking through all my settings.. The standard colour settings for new documents in CS2 were set up to CMYK (Cyan, Magenta, Yellow, Black) rather then RGB (Red, Green, Blue).