plib that is exactly what is happening to me! I get one action or one file transfer, and then it disconnects.
This happens whether I am accessing the KT in windows explorer or calibre.
Have you contacted their customer support? i would be interested to hear what they have to say!
By the way plib, have you tried loading the books onto a microSD card (using a separate card reader) and then putting that into the KT? That is the workaround i have been using for mine so all my books are on the card instead of on the Kobo itself. I just open the MicroSD in Calibre in the "connect to folder" option, and it treats the card as if it is a device.
I am still of course very disappointed that my KT does not work properly :/