Scheduling conflict dialogue box

I get a dialogue box saying "This action will cause a scheduling conflict. Task 68 has a task constraint or is linked to a task that cannot move and as a result the constraint or the link cannot be set." This happens when I try to update % complete column for another task.

I cannot find any constraint on that task [68]. (I'm looking at Task dialogue box - Advanced tab).
That task [68] is a predecessor to another task [71] but 71 also does not have a constraint set.

68 and 71 are both summary tasks.

Is there anywhere else I can find the constraint/link info?

Thanks

RE: Scheduling conflict dialogue box

Thank you for your quick reply.
I hadn't saved a baseline but the task I was trying to mark as 100% complete yesterday had slipped - it had Sept dates in the Start and Finish columns on the plan (not constraints, those were the dates that Project calculated).

The only calendar in the information column is on the final task, product launch. That task uses a non-standard calendar that I created, so the product launch would be scheduled for a weekend only.

Also, the final task has already been marked as complete.

thanks

RE: Scheduling conflict dialogue box

Thanks, sory for the delay I've been away. How do I attach the file?

RE: Scheduling conflict dialogue box

I've emailed the project plan to info with the subject line "FAO: Tanya - scheduling conflict dialogue box enquiry".

I tried using the filter, but that resulted in the task text disappearing and all I could see where the minus boxes that let you hide/show tasks under a summary task.

Thanks
Clare