I'm having this weird thing happen when I mess around with HDR toning in Photoshop. I open my image just as you would regularly, then click on HDR Toning to access its options. I make it look pretty, then hit OK, and my image comes out a grey, ugly mess. I tried switching my bit depth and made sure I wasn't in like CMYK or something for some reason but I get the same effect. Here's a split-screen showing what happens.
I get a similar effect with HDR toning when I set the method to Highlight Compression instead of Local Adaptation. Not sure why it's doing that with you though. You could try applying a second HDR Toning, this time setting it to Equalize Histogram.