Hi Val, hope you are well.
If you've done nothing and just happened to notice this behaviour what this
sounds like is Project's neat way of showing you there is no work being
performed on this task in the time period covered by the dotted lines.
The Gantt bar will automatically change to reflect no work being done on a
task in this way. Take a look at the times each resource will be working on
this particular task and if this is the case, you will be able to see that
there is no actual work being performed over the period covered by the dotted
lines. The Resource Usage view will give you a breakdown of the tasks
allocated to each resource and the hours committed per day to each task. You
can get to this view (in Project 07) by selecting Resource Usage button from
the view bar down the left-hand side of the screen, or by selecting Views ->
More Views -> Resource Usage.
This link provides more information about split task which may be of help to
you:
http://office.microsoft.com/en-au/project/HA101130751033.aspx
It's hard to say how this might have occured if you've just suddenly noticed
it, however it is possible to acheive this if you happen to be tinkering with
resource contours and/or specifying exactly when the work will be performed
by the resource for that particular task.
Hope this helps and you are able to find a resolution in here.
--
Kind regards
Melanie Remen
For more tips on Microsoft Project and Microsoft Project Server, please
visit my blog at:
http://msproject03-2010tips.blogspot.com/