No idea how to fix - I reported the same problem a little while ago and no-one has yet replied - see this --
http://forum.airdroid.com/discussion/14 ... ard#latest
I've been trying again, and it looks as though the error is cosmetic rather than anything else. Just bought a copy of Dark Side of the Moon and used Airdroid to upload it to my Samsung S4 Mini. I got two "Upload failed - no write prermissions for SD card" errors, but checking the phone, it seems that all the tracks were uploaded.
Very annoying though, and a completely new error in my experience - never saw it before the new version.
Paul.