If you have a link to a summary task containing that task then the
dependency between the task which is the predecessor of the summary task and
the tasks under that summary task is hidden. If you have any dependencies
going to summary tasks that is the first place I would look.
You need to look very carefully as the dependency is not visible. Let me
give an example
x is a predecessor to a summary task (we will call it "summary")
a, b, c are tasks under summary and have dependencies a->b->c
x is planned to complete on Sept 1, 2005
If there is no work done on a, b or c then summary starts on sept 2 and "a"
starts on sept 2, followed by b and then c.
However, if there is an actual start on "a" in say July, then "summary"
starts in July. The question is where does "b" start? Well, even though it
only has a dependency on "a", it will not start until Sept 2. If you try to
move it earlier it will spring right back. This may not be what you are
expecting, but since x doesn't finish until then, any of the unstarted tasks
under the summary won't start before x is finished.
Finally (and it should be the first suggestion) go to tools menu / options /
calculation tab and make sure that calculation is set to automatic (or press
F9).
I'd also insert the "actual start" column and make sure that it is clear. It
can have dates even if there is no actual work on the task. That will pin
them in place.
-Jack
