Can't quite figure why the sky turned out like this, help?

Hello to all,

I did an hdr shot of a mural my students did at our Ramsey Field. Not sure why the sky turned out like that though. I just loaded the three photos into photomatix and that's what popped up. I tried dodging and burning but couldn't fix it pass this without ruining it. I could have tried layering and masking but I haven't figured out how to do those yet, lol. Any help I could get from any of you would be appreciated.

http://www.flickr.com …nio_quichocho/4​670846420/

Thanks,
Antonio