Android 2.3 and 4 MTP - Synching Files with Rhythmbox

[pi6502]

Hello,

currently I'm copying music to my rooted android 2.3.6 smartphone's SD card with Rhythmbox -- as soon as I connect the smartphone in USB mode to the PC and mount the SD card, I see it as device in my Rhythmbox player -- works like a charm
My new Smartphone will have android 4.x -- today I tried to convince a friend of mine that is easy to manage music library with ubuntu and android. My friend's phone was a not rooted Sony Xperia J (I'll purchase the Sony Xperia L). I tried both MTP (I have gvfs-mtp installed from Philip Langdale), and MSC on his smartphone -- the former is seen by Rhythmbox, but attemps to drag and drop music to it results into application crash, the latter mounts as mass storage device; I cannot drag and drop in Rhythmbox because it is not recognized as media device, but I can move files wtih gnome comander or the like.
Note that I can copy files in MTP mode as well -- what crashes is the capability of the media device in Rhythmbox, hence the drag and drop thing.

How come that my rooted phone works perfectly with rhytmbox? Has something changed in Android's SD partitioning mechanism? How can I enable smooth drag and drop within my favourite music player again? The idea to fall back to file copy with my new Xperia L is not nice.

Thanks,
#pi4630

p.s.: I am using ubuntu 12.04. 64 bit -- could not update my profile!