That yellow bar is caused by the Bluetooth app
When the Bluetooth is on, within the yellow bar there is now a message telling you that download's folder may be used to receive files over bluetooth:http://s2.subirimagenes.com/imagen/previo/thump_8887358screenshot.png
If you click on preference, you will see again that Download's folder is set to receive files from Bluetooth.
The problem is, when Bluetooth is disabled, the message disappear, but the yellow bar remains:http://s2.subirimagenes.com/imagen/previo/thump_8887365screenshot1.png
Now, I guess that's a bug, and I don't know how to fix it, but, instead of fix the bug you can do 2 things:
Change the folder for Bluetooth's files to one you never use (I don't know how neither)
What I did: Uninstall the Bluetooth app with:
sudo apt-get purge mate-bluetooth
And if you need to use bluetooth you can try others apps like blueman
i haven't prove to send files or connect a Bluetooth device yet, so I can't promise that blueman is gonna work, but at least after install it, there is no yellow bar.
I hope that can help you, and if you like, you could report that bug to lmde or mate developers (I don't know how).