1. Backup logs. You can find these on your WHS in C:\Documents and Settings\All Users\Application Data\Microsoft\Windows Home Server\logs, named backup-mmddyy.log.
2. WHS eventlogs; on your WHS do Start, Run, type eventvwr.msc, Hit Enter.
3. Client eventlogs
Best thing to start however would be to run chkdsk D: /f /r from a command prompt on the client PC