It's most likely software. I have this same issue with the 1520 in my car with a clarion CX501 (that had ZERO issues with my WP7.8 Focus S), but I do not have this issue with the 1520 in my other car that has a pioneer p80rs. With the pioneer I could not skip tracks like on my Focus S until I updated its firmware (even though the updated firmware was a year old, it added this feature).
I've googled this extensively and it's just the way the particular combination of phone software, firmware, and audio hardware/firmware. Update the firmware on your Samsung and see if that helps!