Thank you for your suggestions. I have tried kernel 3.9.0-030900rc5-generic, and the computer has now been running for 5 days! (Previously the problem would have surfaced after a day or two). I had some issues initially after booting: it would boot but when trying to login the session would hang whilst running .profile, so I think it's not completely working. I've just had another instance of: niu 0000:09:00.0: eth2: Transmit timed out, resetting This time though eth2 recovered and the network is still functioning, so that's an improvement but not a complete solution. I don't know whether that means the problem is fixed or not, so I don't know whether to tag "kernel-bug-exists-upstream" or "kernel-fixed-upstream" (or even "kernel-unable-to-test-upstream" given the initial problems). Here's the syslog: Apr 10 02:58:58 metope2 kernel: [388060.816009] ------------[ cut here ]------------ Apr 10 02:58:58 metope2 kernel: [388060.816031] WARNING: at /home/apw/COD/linux/net/sched/sch_generic.c:255 dev_watchdog+0x262/0x270() Apr 10 02:58:58 metope2 kernel: [388060.816037] Hardware name: SUN FIRE X2250 Apr 10 02:58:58 metope2 kernel: [388060.816039] NETDEV WATCHDOG: eth2 (niu): transmit queue 7 timed out Apr 10 02:58:58 metope2 kernel: [388060.816042] Modules linked in: nfsv3 autofs4 nfsd nfs_acl auth_rpcgss nfs fscache lockd sunrpc tpm_infineon xt_hl ip6t_rt nf_conntrack_ipv6 nf_defrag_ipv6 ast ipt_REJECT xt_LOG ttm xt_limit drm_kms_helper drm xt_tcpudp xt_addrtype coretemp kvm_intel kvm i2c_algo_bit nf_conntrack_ipv4 nf_defrag_ipv4 xt_state sysimgblt sysfillrect ip6table_filter gpio_ich ip6_tables syscopyarea microcode ioatdma nf_conntrack_netbios_ns nf_conntrack_broadcast nf_nat_ftp nf_nat i5400_edac tpm_tis lpc_ich nf_conntrack_ftp edac_core nf_conntrack psmouse dca shpchp i5k_amb joydev serio_raw iptable_filter mac_hid lp ip_tables parport x_tables hid_generic usbhid hid raid10 raid456 async_pq async_xor xor async_memcpy async_raid6_recov e1000e ptp pps_core raid6_pq async_tx niu raid1 raid0 multipath linear Apr 10 02:58:58 metope2 kernel: [388060.816126] Pid: 0, comm: swapper/1 Tainted: G I 3.9.0-030900rc5-generic #201303311835 Apr 10 02:58:58 metope2 kernel: [388060.816133] Call Trace: Apr 10 02:58:58 metope2 kernel: [388060.816136] [] warn_slowpath_common+0x7f/0xc0 Apr 10 02:58:58 metope2 kernel: [388060.816147] [] warn_slowpath_fmt+0x46/0x50 Apr 10 02:58:58 metope2 kernel: [388060.816156] [] ? wake_up_worker+0x24/0x30 Apr 10 02:58:58 metope2 kernel: [388060.816163] [] dev_watchdog+0x262/0x270 Apr 10 02:58:58 metope2 kernel: [388060.816169] [] ? __queue_work+0x2a0/0x2a0 Apr 10 02:58:58 metope2 kernel: [388060.816172] [] ? pfifo_fast_dequeue+0xe0/0xe0 Apr 10 02:58:58 metope2 kernel: [388060.816180] [] call_timer_fn+0x46/0x160 Apr 10 02:58:58 metope2 kernel: [388060.816185] [] run_timer_softirq+0x267/0x2c0 Apr 10 02:58:58 metope2 kernel: [388060.816191] [] ? read_tsc+0x9/0x20 Apr 10 02:58:58 metope2 kernel: [388060.816198] [] ? pfifo_fast_dequeue+0xe0/0xe0 Apr 10 02:58:58 metope2 kernel: [388060.816205] [] __do_softirq+0xd8/0x270 Apr 10 02:58:58 metope2 kernel: [388060.816209] [] irq_exit+0x96/0xb0 Apr 10 02:58:58 metope2 kernel: [388060.816216] [] smp_apic_timer_interrupt+0x6e/0x99 Apr 10 02:58:58 metope2 kernel: [388060.816221] [] apic_timer_interrupt+0x6d/0x80 Apr 10 02:58:58 metope2 kernel: [388060.816224] [] ? hrtimer_start+0x18/0x20 Apr 10 02:58:58 metope2 kernel: [388060.816236] [] ? native_safe_halt+0x6/0x10 Apr 10 02:58:58 metope2 kernel: [388060.816243] [] default_idle+0x45/0x120 Apr 10 02:58:58 metope2 kernel: [388060.816246] [] cpu_idle+0xd9/0x120 Apr 10 02:58:58 metope2 kernel: [388060.816251] [] start_secondary+0xc3/0xc5 Apr 10 02:58:58 metope2 kernel: [388060.816254] ---[ end trace 4a1e57573edccef8 ]--- Apr 10 02:58:58 metope2 kernel: [388060.816260] niu 0000:09:00.0: eth2: Transmit timed out, resetting