Low disk space message at the starter

I have ubuntu 9.10 installed on a bgb Kingsone USB Drive, Avery time I will start it I will get this message: "Low disk space: this computer has only 26.5 MB disk space remaining.You can free.........."
and when I check in System Monitor there only 1.9 gb used and 5.6.

ProblemType: Bug
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 2/2
   Subdevice #0: subdevice #0
   Subdevice #1: subdevice #1
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ubuntu 4405 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xdf300000 irq 22'
   Mixer name : 'Nvidia MCP78 HDMI'
   Components : 'HDA:111d76b2,103c3603,00100302 HDA:10de0003,10de0101,00100000'
   Controls : 39
   Simple ctrls : 23
CheckboxCommand: alsa_record_playback
CheckboxDescription:
 Open the volume control application by right-clicking on the speaker icon in the panel and selecting "Sound Preferences". Select the "Input" tab and choose any alternate (non-default) device(s). Select the "Output" tab and choose any alternate (non-default) device(s). When you are done, click the Test button, then speak into the microphone. After a few seconds, your speech will be played back to you.

 Did you hear your speech played back?
CheckboxTest: alsa_record_playback_alternates
Date: Fri Dec 25 07:21:01 2009
DistroRelease: Ubuntu 9.10
LiveMediaBuild: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
Package: alsa-base 1.0.20+dfsg-1ubuntu5
PackageArchitecture: all
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.UTF-8
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
SourcePackage: alsa-driver
Tags: checkbox-bug
Uname: Linux 2.6.31-14-generic i686
XsessionErrors:
 (gnome-settings-daemon:4459): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (gnome-settings-daemon:4459): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (nautilus:4515): Eel-CRITICAL **: eel_preferences_get_boolean: assertion `preferences_is_initialized ()' failed
 (polkit-gnome-authentication-agent-1:4546): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed