Version:           4.0 (using KDE 4.6.5) 
OS:                Linux

I had one big Ext4-partition (with size about 2.7 Tb) in GPT-labeled HDD.
I use [Partition usage] --> [Table (listview)] for watch the FS usage. The [Used] and [Available] sizes show correctly (675.4 Gb, 1.9Tb), but total size show incorrectly negative value -1 410 683 688 Kb instead 2.7 Tb.

The du command worked correctly:
[Amin@AminCave /]$ df -h | grep 3T
/dev/sda1             2,7T  676G  1,9T  26% /mnt/Hit_3Tb

Reproducible: Always

Steps to Reproduce:
1). Create one big Ext4 partition on "3Tb" HDD with GPT (ms-dos MBR can't this).
2). Make mkfs.ext4 and mount it.
3). Watch total size in KSysGuard --> [Partition usage] --> [Table (listview)] for big partition.

Actual Results:  
Total size = -1 410 683 688 Kb

Expected Results:  
Total size = 2.7 Tb

OS: Linux (i686) release 2.6.35.13-91.fc14.i686.PAE
Compiler: gcc

[root@AminCave /]# fdisk -l /dev/sda

WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted.

Disk /dev/sda: 3000.6 GB, 3000592982016 bytes
255 heads, 63 sectors/track, 364801 cylinders, total 5860533168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1  4294967295  2147483647+  ee  GPT


[Amin@AminCave /]$ df | grep 3T
/dev/sda1            2884283608 708171228 2029599128  26% /mnt/Hit_3Tb