Hpdb, I can understand your frustration. I have been a DD user for the last three years and have run into problems from time to time but was able to get them solved with help from DD support. Maybe I have run into your problem before so if you would like for me to offer some suggestions, I would be glad to try and help.
What are you mapping on this 50 acre plot; flat grassland, agriculture, construction project, land with lots of water? What is the altitude and overlap settings for this 50 acre project? What engine are you using to upload jpegs; Chrome, Firefox, Safari?
If you would rather speak to me in person, please feel free to do so. I will try my best to help.