I reconnected a host that has been down for a while and now it shows negative credit for the day it restarted activity. There were no unfinished tasks on the machine during the pause.

The negative credit shows up only on the summary page:
http://boincstats.com/stats/boinc_host_graph.php?pr=bo&id=f776ec1c3d75009dd2ae969e6cffd143
not in the details of any project.
This is the host: http://boincstats.com/bam/account_host.php?host_id=133479