We're having our employees enter in their hours using Project Central.  Today, it seems that hours for the past few weeks that were entered into the system have magically disappeared.  I can't figure out why.  

Some background:
My company is also using Project Central as a pseudo timetracking system.  As a result, many tasks that are non-stop and continuous are being entered into the Gantt chart so that hours can be logged against them.  We did not want to use the "Recurring Task" feature as this resulted in a long list of the same task when someone would log into Project Central.  Instead, we just set such tasks to have very many hours attributed to them so that they were never "overdue".  However, this messed up the resource allocations.  To overcome this, we decided to set such tasks to zero hours in duration and just put up with the "overdue" signs.  However, after I changed the duration to zero, some of the people's hours that were entered in for tasks seemed to have magically disappeared into thin air.  It should be noted that this happened to only some people, not all, although there doesn't seem to be any type of criteria that decides who gets deleted hours and who doesn't.  There was absolutely no warning from the program when I changed the task durations to zero that anything would be deleted from Project Central in terms of the hours already submitted.

Can anybody shed a light on this?  
You can reach me at angie_hung@hotmail.com