You have done this before with no problem?
There are a couple of problematic things shown in your screen shots -
1) Your Sequence is set to H.264 - FCP 6 does not work correctly with H.264. As pointed out by frequent forum contributor Shane Ross, unfortunately FCP will appear to work with H.264, but it really does not work reliably. Try switching the Sequence QuickTime Video Settings Compressor setting to ProRes. If you need to end up with an H.264 file, you can export the finished sequence in that format.
2) Is you source clip that you have posted an images sequence or an individual tiff still? FCP works with stills that are less than 4000 pixels in the widest dimension, in RGB Color, 8bits/channel. Check to make sure your source image meets these requirements.
MTD