Ah...good.
And yes expect that concerning hooking up your n810 to your pc while running turbo from the card.
It is due to being "in use"
You should be able to transfer files via wifi, bluetooth ...even take the sd card out of the n810 (only when shut down) and in a linux pc transfer files to the partition which has folders for the file system (ie: documents, downloads, etc)

There are a few downsides to running off the n810 sd card
such as your attempt to transfer to the running system off the card.
And being a bit more frugal with sd card space if one wished to have multiple os's on the same card....
compared to say the n800 (which with the internal sd card slot allows for much more play concerning multiple os's and no problem transferring to the external card slot ...as long as the usage of it is for storage.)

Just have to be frugal with the space you have if you wish to experiment with multi booting...to allow enough space for other os's.

There are also other options for various operating systems that don't need such usage.
But you will discover them.