Project is inserting a task with the resource name when I assign a resource - why is it doing this?

[Stubobster]

When I assign a resource to a task in my Gantt in MS Project 2010, it is inserting/creating a new task line below that task and inserts the RESOURCE NAME in that line. What is causing this? Is it a setting or is my file corrupt? I did not configure it that way. Thanks!

 

[JulieInMaine]

This is certainly not normal behavior. Does it happen in all files or just one?