[HELP] data corruption: swap of bytes distant from 12 bytes

When I download huge files from the net (e.g. disc images), they
often come slightly corrupted. I have analysed the corruption in
detail (comparing the corrupted file with a known good one) and
find the corruption is allways a swap of bytes distant from exactly
12 bytes; This corruption comes seemingly at random, though very
often in burst of 2 or 4 consecutive bytes. Typical errors would be

address ref err

000F2382: 00 08
000F238E: 08 00
...
022D3DDE: 2E 6E
022D3DDF: 63 64
022D3DE0: 61 65
022D3DE1: 63 78
...
022D3DEA: 6E 2E
022D3DEB: 64 63
022D3DEC: 65 61
022D3DED: 78 63

Configuration
- MSI KT3 ultra2 (MS6380-E), Athlon XP2100, standard bios settings
- 80GB IDE Seagate HD (x2), ATI 8500LE, 1GB RAM
- Netgear PCI FA310TX (x2) 10/100BT Ethernet cards
- Window XP + all patches, standard drivers for
- 10BT hub
- cable modem (Motorola, ethernet interface, DHCP)

Corruptions occurs
- with several download servers
- with either ftp or http
- with either Explorer or Opera
- with either of the two 10/100BT Ethernet cards
- with firewall/connection sharing on or off

I never had any corruption with another computer (Macintosh)
hooked on the same hub/cable modem, thus believe the problem
is with the PC/Netgear PCI F310TX/drivers

Any clues?

Francois Grieu