Sorry its been a while since I've given any feedback, but I come bearing gifts. I've looked into the reason why the default Media Player doesn't skip and its because they use MAFW.

Apparently this can circumvent the patches and makeshift changes that you've tried to correct the lockscreen stuttering and play music in Silent Profile. Here's an excerpt I found from the website below:

"Using MAFW on the N900 has some benefits. For instance, audio will play in silent mode and doesn't stutter while locking the screen. And you are able to control the volume with the hardware keys while the screen is locked (this requires Maemo5 PR 1.2)."

http://pycage.blogspot.com/2010/06/n...n900-n800.html

If you take a look at that site, he also has the source code posted in the Garage for scripting MAFW in Python. So I'm hoping this can be of some kind of help to you. Best of luck!