Looks like you have a lot of chromatic aberration in the trees in the lower part of the picture and left hand side where the tree branches are, I don't think the branches should be green. This could be from the original images, or a result of the HDR processing. I believe that one of the options in Photomatix on the Option screen is "Reduce chromatic aberrations" - I don't know if you checked this or not, but if you didn't, then you might want to try this again with that box checked. If that does not work, then you may have to process each image separately to remove it. Also, the sky looks blown out a bit and the clouds look yellow in places, so I am not sure where these affects all come from, but that is my initial reaction. Sorry if this seems a little harsh.
Regards,
WesternGuy