Intermittent system crash apparently due to ethernet card or driver

[Seakat]

Hi,

I am running Ubuntu 14.04 LTS (in French).
The problem I'm reporting has occurred intermittently over the past 5 
months or so, with kernels 3.13.0-69 generic to 77 generic. It has 
occurred with two different modems,
First with a TP-LINK Router/modem WN822N TL-WR842N (bought and used in 
China)
Second with a France Telecom-Orange Livebox-198c, hired from Orange in 
France and used in France).

I have a Acer ASPIRE 5735Z laptop (bought end 2009).
Memory: 3.9 GO
Processors: Pentium (R) Dual Core CPU T4200 @ 2 GHz x 2
Video card: Mobile INTEL (R) GM45 Express chip set x86/MMX/SSE2
OS: 32 bits
Disk 287.9 Go

Crashes occur when I have cable connection to a modem, The screen 
switches to terminal mode and the machine stops;
What is written on the screen varies slightly, but generally starts with:
"[1350796098] BUG - Unable to handle kernel NULL pointer reference at 
0000050d
Sky2_hw_error_+0x126/0x15c [sky2]"

Lower down the screen I get a line with "kernel panic", and a couple of 
lines later it stops.

I guess it's something to do with my Marvell YUKON network card or the 
driver, but what to do?

Cheers,