Motion timeline length

Is anyone else experiencing this. All of my motion files are locked at 300 frames. Now before someone tells me that is the default i know that but here is the weird thing. I create a ntsc comp and set the project length to 20 seconds. I make my necessary edits and save my file. All is well. I import the file into FCP and lay in the timeline and it states it is 20 seconds long. All is still well. Now, Let's say i want to edit the original motion file. I right click on the motn file in the timeline and select "edit in editor" and the file opens back up in motion, but now, my timeline length is locked back at the default of 300 frames (10 seconds). i thought it might be a problem with a corrupt file so i made a new one (DVD menu) and placed that in DVDSP, time looked fine. Again, i go back in and try to edit the file and it is again locked at 300 frames. I've tried to open the file from within motion and it still goes back to the default file length.

Is this happening to anyone else?