I run this project with 4 other projects (24/7) using BOINC 6.4.5. I didn't have this problem before I downloaded this new version of BOINC very recently.
I lost my work a day or two ago (I had over 21% completed in just over a month) due to this error when I reset the project. I didn't think it would delete my work unit. Today, after running the new work unit it downloaded, I again received the same message repeatedly. Here is what it reads:

Visual Fortran run-time error

forrtl:severe(3:error during write,unit 8, file

C:\ProgramData\BOINC\projects\climateprediction.net\hadsm3fub_k6pq_005973489\tmp\pipe_dummy

Image PC Routine Line Source
hadsm3_um_6.07_wi 0064C8A2 Unknown Unknown

Stack trace terminated abnormally

I moved your post from the CPDN notifications thread to its own thread, to keep that other thread uncluttered and available for CPDN news only.

As for what you should do, best report this problem on the CPDN forums. You'll get quicker help there than having to wait for one of the CPDN people to stroll past these forums.

This isn't a BOINC problem as BOINC doesn't use the Fortran programming language.

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If you use the link that Ageless provides, and use Advanced search (at the top), to look for Fortran, and also forrtl, using the 1 year time scale, you'll find quite a few posts about the problem.
However, there's no definitive answer.
It doesn't seem to have happened to any of the people who regularly answer questions there, just some possibilities. Perhaps those that have found an answer never return to tell us.

The closest someone has gotten to fixing it for themself, is here.