Similar here too.  The machine disappears from the network until reboot.  The card is

01:01.0 Ethernet controller: 3Com Corporation 3c905C-TX/TX-M [Tornado] (rev 78)
        Subsystem: 3Com Corporation 3C905C-TX Fast Etherlink for PC Management NIC
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr- Stepping- SERR- FastB2B-
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
        Latency: 64 (2500ns min, 2500ns max), Cache Line Size: 16 bytes
        Interrupt: pin A routed to IRQ 21
        Region 0: I/O ports at b800 [size=128]
        Region 1: Memory at e7dffc00 (32-bit, non-prefetchable) [size=128]
        Expansion ROM at 50000000 [disabled] [size=128K]
        Capabilities: [dc] Power Management version 2
                Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
                Status: D0 PME-Enable- DSel=0 DScale=2 PME-

The first sign of the problem in syslog is

Jun 23 05:36:51 bettyboop kernel: [585849.763346] NETDEV WATCHDOG: eth0: transmit timed out
Jun 23 05:36:51 bettyboop kernel: [585849.763356] eth0: transmit timed out, tx_status 00 status 8601.
Jun 23 05:36:51 bettyboop kernel: [585849.799305]   diagnostics: net 0cc6 media 8880 dma 0000003a fifo 0000
Jun 23 05:36:51 bettyboop kernel: [585849.838385] eth0: Interrupt posted but not delivered -- IRQ blocked by another device?
Jun 23 05:36:51 bettyboop kernel: [585849.886389]   Flags; bus-master 1, dirty 3633675(11) current 3633675(11)
Jun 23 05:36:51 bettyboop kernel: [585849.927012]   Transmit list 00000000 vs. ffff81003de608e0.
Jun 23 05:36:51 bettyboop kernel: [585849.960383]   0: @ffff81003de60200  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585849.998432]   1: @ffff81003de602a0  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.036482]   2: @ffff81003de60340  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.074531]   3: @ffff81003de603e0  length 8000005f status 0c01005f
Jun 23 05:36:51 bettyboop kernel: [585850.112582]   4: @ffff81003de60480  length 8000005f status 0c01005f
Jun 23 05:36:51 bettyboop kernel: [585850.150632]   5: @ffff81003de60520  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.188682]   6: @ffff81003de605c0  length 8000005f status 0c01005f
Jun 23 05:36:51 bettyboop kernel: [585850.226732]   7: @ffff81003de60660  length 8000005f status 0c01005f
Jun 23 05:36:51 bettyboop kernel: [585850.264782]   8: @ffff81003de60700  length 8000002a status 0001002a
Jun 23 05:36:51 bettyboop kernel: [585850.302832]   9: @ffff81003de607a0  length 8000002a status 8001002a
Jun 23 05:36:51 bettyboop kernel: [585850.340882]   10: @ffff81003de60840  length 8000002a status 8001002a
Jun 23 05:36:51 bettyboop kernel: [585850.379452]   11: @ffff81003de608e0  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.418021]   12: @ffff81003de60980  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.456591]   13: @ffff81003de60a20  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.495160]   14: @ffff81003de60ac0  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.534142]   15: @ffff81003de60b60  length 800005ea status 0c0105ea
Jun 23 05:36:51 bettyboop kernel: [585850.572717] eth0: Resetting the Tx ring pointer.