Today I had the same problem and nobody in the German FCP could help me.
I just repaired the user right with the disk disk service software and – STRIKE! – it works. Now FCP adds the suffix .mov to the clips in the directory during the capturing and the HDV capturing works with the regular logg-window with app. 3 MB per second (by using the Apple pro res codec the files are nearly 9 MB per sec., now the rendering is much more faster).