Final Cut Pro X - erroneous "flash" clip
I am trying to create a project and for some reason Final Cut Pro X will mask/copy (whatever) a brief second of a still several frames before and add it to a frame further down the line. I have gone back numerous times and tried deleting the still that it is copying but the program still insists on inserting it even without the original even being on the timeline. The flash of the still wouldn't be more than a split second but it is absolutely annoying and unacceptable. Has anybody else had this problem and, if so, how does one solve it? This is the second time I have restarted this project only to find the same problem but with different stills. I thought that it might have been due to the copying of a crossfade transition. However, I have deleted all those, plus the original offending still to no avail. Please can somebody help me?
Thank you
MItaka27
Final Cut Pro 7, Mac OS X (10.6.7)