Both of my climate prediction tasks just failed with the error above. Can they be recovered and restarted, or do new tasks have to be downloaded?

Yes, failed models can often be recovered, using backups made in anticipation BEFORE the failure.
See my sig for details.

Otherwise, you'll have to try and get new work from the VERY little that's currently available.
See my post here about the availability of work.

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Backups: Here

As all three models on that computer have failed, it may be worth checking some of the known causes of crashes before downloading any more. - Running memtest to ensure it is not a faulty memory problem that only show up under the intensive load cpdn puts on some machines, making sure the boinc data directory is excluded from any virus scans as they can put a lock on the file when boinc needs to write to it. Also on my machine the odds improve if I suspend work units and exit boinc before turning machine off. Not quite sure if this last one is relevant under windows or just linux.

Dave

Suspending and exiting from Boinc before shutdown is relevant in Windows. You can loose a model if the shutdown catches it at a crucial moment such as when it is writing to the disk.

Oh for an intelligent OS that will shut everything down cleanly before closing itself down!

Unfortunately, that would require "slow and careful", and people want "Faster! Faster!", which is what is happening with each new version of Windows. :(
Sometimes people just have to include themselves in the loop.

The problem with this project, is that there's a LOT of ancillary files open, all of which need to be shut down. I think that the problem mainly occurs if shut down occurs while the files are being saved at a checkpoint, and only some have been saved. Then some of them are out of sync with the others, and the program can't restart.

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Backups: Here

I normally do 'File | Exit BOINC' and tell it that I do want to stop running science applications. That seems to work OK, but maybe I have been lucky.

Do I need to do something else before doing that (suspend the CPDN tasks in the task tab or the CPDN project in in the project tab)?

Thanks

That's prudent and proper, so boinc should "do right" every time.

As an extra measure of caution, I developed the habit, years ago, of clicking "Suspend" in boinc "Activity" before "File/Exit." (As you are aware, having been around since 2007, we used to run some really long tasks and there was no such thing as being too safe.)

Cheers, Randi.

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"We have met the enemy and he is us." -- Pogo
Greetings from coastal Washington state, the scenic US Pacific Northwest.

Thank you!