Binary package hint: dolphin
If you have a real huge image a folder dolphin trys to create a thumbnail. It allocates a lot of memory (surprise, surprise) and at some point it starts to swap. When this point is reached your system goes unstable and you are happy if you don't need to kill X.
Summary:
Put some real huge image in Folder open it in dolphin and press preview. I used a 105M big png.
Images to be found at http://visibleearth.nasa.gov/view_detail.php?id=7100
Output of Top:
top - 14:24:35 up 3:46, 1 user, load average: 8.40, 2.90, 1.24
Tasks: 183 total, 3 running, 179 sleeping, 0 stopped, 1 zombie
Cpu(s): 2.0%us, 4.2%sy, 12.9%ni, 12.4%id, 68.1%wa, 0.1%hi, 0.4%si, 0.0%st
Mem: 2072324k total, 2017972k used, 54352k free, 1036k buffers
Swap: 4690972k total, 1686748k used, 3004224k free, 88448k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
12256 georg 25 5 1839m 619m 5048 D 23 30.6 0:24.18 kio_thumbnail
12253 georg 25 5 1840m 598m 5072 R 21 29.6 0:14.94 kio_thumbnail
12257 georg 25 5 1839m 397m 4960 R 14 19.6 0:13.42 kio_thumbnail
Which version of Dolphin and Kubuntu are you using? Thanks.