The only other trick that might work is to try and find your flight combos at hipmunk.com (my newest favorite site)

It will then give you buttons to try and book on all the websites it thinks it can (e.g. one button for af.com, another for klm.com, another for delta.com -- if possible)

Go through each website and see what happens. I usually get lucky with pricing funny-business like this on klm.com after delta and af.com fail.