Main task shows 99% but all Sub-Tasks are 100%?

I've completed all the sub-tasks for a task and put them all to 100% and marked them Complete. The main tasks still shows 99% though. I've went back over the tasks and entered them as 100% again, but it still doesn't show. I've marked a sub-task down to zero, and the main task drops according. But, when I put the sub-task back to 100...the main task still shows 99%?