Theirry, the "no finished file" message means the manager temporarily lost track of the daemon. The daemon (which actually controls the work) should have kept running. It's just reporting the manager (the part you see) lost contact.

tony

OK... and that's why the Calculation time drop from 32 minutes to 18 minutes?

No, I suppose that's because between 18 and 32 minutes runtime there was no checkpoint. Checkpoints occur every 5 - 30 minutes depending on the WU and the speed of your computer (on slow computers it might even take longer in rare cases).