[PROBLEM] No space available for update

[aitor]

Software
XBian version: 1.0RC3
XBMC version: 13.2
Overclock settings: default

Hardware
RPi model: B 512
SD card size and make/type: 8Gb
Network: Wireless
Connected devices: TV, USB HD.

Problem description:
I'm trying a system update from xbian-config, but I get an error message:

Code:

E: Write error - write (28: No space left on device)

My SD card is:

Code:

Filesystem     Type      Size  Used Avail Use% Mounted on
rootfs         rootfs    7.1G  6.7G  202M  98% /
/dev/mmcblk0p2 btrfs     7.1G  6.7G  202M  98% /
devtmpfs       devtmpfs  171M  4.0K  171M   1% /dev
none           tmpfs      36M  156K   36M   1% /run
/dev/mmcblk0p2 btrfs     7.1G  6.7G  202M  98% /home
/dev/mmcblk0p2 btrfs     7.1G  6.7G  202M  98% /lib/modules
/dev/mmcblk0p1 vfat       34M   20M   15M  57% /boot
/dev/sda1      ext4      917G  849G   22G  98% /media/biblio_HD
/dev/mmcblk0p2 btrfs     7.1G  6.7G  202M  98% /xbmc-backup

Maybe, I can try a new installation from scratch, lossing my configuration, but, are there another way to do it? Any idea?

Thank you.