Why: Your computer simply did not return a valid result. As you can see from the sterr_out I posted above from one of the tasks your PC crunched, there was no output file. The project validator saw that work was at least attempted and gave you 20 instead of 0.

Now, since it's happening consistently there are several things that could be happening.

1. Check "leave applications in memory when suspended" in BOINC, under Tools -> computing preferences. Disk and memory usage tab.

2. You have such a small resource share set for Rosetta that it switches to another project before it checkpoints, saving no data for work performed. This is just a guess, as you have a reasonably modern PC and only 3 total results showing in the database.

3. Frequent reboots or otherwise exiting and restarting BOINC.

4. Unlucky with bad tasks. Someone else has said on here that they always have trouble with hyb* series tasks. I haven't noticed any problems when I run them, so I can't be of any help there.

I'm sure I'm leaving some other possibilities out but there's a start.

Check this thread.

I will not be drawn in to a credit value discussion, but I did want to point out that if you believe the credits are truly your only reward and return on investment, then you are missing the point of Rosetta@home. The point being that you have helped conduct research that may save your life some day. And when there is another worldwide pandemic or epidemic, indeed it may some day prevent a virus from killing 30% of the world's population the way the black plague did.