Receiver / sender disabled?

Hi :-)

I have a problem with a Realtek RTL8139C Card:

First a little history about this card: I worked for about half a year 
without any mayor problems, but around New Years Eve it started to have 
dropouts and a few hours later it completly refused to work. Sidenote: I 
don't have directly access to the computer, so I can only tell you what I 
see through a ssh session.

I use Redhat-7.3 with the "standard" 8139too driver. But to have a common 
base, I installed Don's rtl8139 driver and rtl8139-diag. This is what I get 
in the logs when I reboot the machine:

kernel: pci-scan.c:v1.11 8/31/2002  Donald Becker <[email protected]> 
http://www.scyld.com/linux/drivers.html
kernel: rtl8139.c:v1.22 11/17/2002 Donald Becker, [email protected].
kernel:  http://www.scyld.com/network/rtl8139.html
kernel: divert: allocating divert_blk for eth0
kernel: eth0: RealTek RTL8139C Fast Ethernet at 0xdc00, IRQ 10, 
00:50:fc:61:8b:2f.

And about one minute later:

kernel: eth0: Transmit timeout, status 11 0000 media 14.
kernel: eth0: Tx queue start entry 4  dirty entry 0, full.
kernel: eth0:  Tx descriptor 0 is 00002000. (queue head)
kernel: eth0:  Tx descriptor 1 is 00002000.
kernel: eth0:  Tx descriptor 2 is 00002000.
kernel: eth0:  Tx descriptor 3 is 00002000.
kernel: eth0: MII #32 registers are: 9000 7809 0000 0000 01e1 0000 0000 
0000.

rtl-diag reports this:

rtl8139-diag.c:v2.10 9/18/2002 Donald Becker ([email protected])
 http://www.scyld.com/diag/index.html
Index #1: Found a RealTek RTL8139 adapter at 0xdc00.
Realtek station address 01:01:01:01:01:01, chip type 'rtl8139C'.
  Receiver configuration: Reception disabled
     Rx FIFO threshold 16 bytes, maximum burst 16 bytes, 8KB ring
  Transmitter disabled with normal settings, maximum burst 16 bytes.
  Flow control: Tx disabled  Rx disabled.
  The chip configuration is 0x14 0x0c, MII half-duplex mode.
  No interrupt sources are pending.

Any Ideas? Is the network card broken? Or the cable? Or the switch port?

Best regards,
Okke.