I have the same problem, anytime I enter the media server on the xmb, the program quits immediately on my ubuntu and the ps3 gives the 2101 error. I checked it and there is noting in the log file of the media server. the last entry is about discovering and finding the ps3.
I use internet connection sharing with firestarter to connect my destkop pc to my ps3. maybe this is the error?? however it worked with windows xp with the same connection sharing.
Does anyone have any idea how to resolve this issue?