It seems this is a recurring issue, see #855199. The problem is that the irqfixup code gets broken. There is of course an underlying problem of spurious interrupts but booting with the irqpoll option should handle this. It worked for awhile but seem to have reoccured from at least kernel 3.2.0-39 in precise, possibly earlier.

I am now running quantal 3.5.0-27 and the problem remains. If the wrong IRQ gets disabled the system gets sluggish and needs rebooting. It is extremely frustrating. I am running an AMD Fusion board:
 Example dmesg output:
[    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-3.5.0-27-generic root=UUID=fc511922-937e-4b41-a891-3667495fa66e ro irqpoll irqfixup                         
[    0.000000] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.5.0-27-generic root=UUID=fc511922-937e-4b41-a891-3667495fa66e ro irqpoll irqfixup   
....
[37805.735959] irq 16: nobody cared (try booting with the "irqpoll" option)
[37805.737619] Pid: 2457, comm: kvm Not tainted 3.5.0-27-generic #46-Ubuntu
[37805.737623] Call Trace:
[37805.737627]  <IRQ>  [<ffffffff810e1a6d>] __report_bad_irq+0x3d/0xe0
[37805.737646]  [<ffffffff810e1f32>] note_interrupt+0x1c2/0x210
[37805.737665]  [<ffffffffa059b0d2>] ? __nf_conntrack_alloc+0x72/0x2f0 [nf_conntrack]
[37805.737673]  [<ffffffff810df6d7>] handle_irq_event_percpu+0xa7/0x1f0
[37805.737683]  [<ffffffffa059b0d2>] ? __nf_conntrack_alloc+0x72/0x2f0 [nf_conntrack]
[37805.737689]  [<ffffffff810df86e>] handle_irq_event+0x4e/0x80
[37805.737694]  [<ffffffff810e2a6a>] handle_fasteoi_irq+0x5a/0x100
[37805.737701]  [<ffffffff81015082>] handle_irq+0x22/0x40
[37805.737708]  [<ffffffff8168b6ca>] do_IRQ+0x5a/0xe0
[37805.737716]  [<ffffffff81681c6a>] common_interrupt+0x6a/0x6a
[37805.737724]  [<ffffffff8116e484>] ? kmem_cache_alloc+0x64/0x130
[37805.737733]  [<ffffffffa059b0d2>] __nf_conntrack_alloc+0x72/0x2f0 [nf_conntrack]
[37805.737742]  [<ffffffffa059b877>] nf_conntrack_in+0x527/0x8b0 [nf_conntrack]
[37805.737751]  [<ffffffffa05af421>] ipv4_conntrack_in+0x21/0x30 [nf_conntrack_ipv4]
[37805.737757]  [<ffffffff8159c3a4>] nf_iterate+0x84/0xb0
[37805.737775]  [<ffffffffa04b1870>] ? br_nf_pre_routing_finish_ipv6+0x140/0x140 [bridge]
[37805.737780]  [<ffffffff8159c444>] nf_hook_slow+0x74/0x130
[37805.737790]  [<ffffffffa04b1870>] ? br_nf_pre_routing_finish_ipv6+0x140/0x140 [bridge]
[37805.737799]  [<ffffffffa04abe70>] ? br_handle_local_finish+0x50/0x50 [bridge]
[37805.737810]  [<ffffffffa04b2a58>] br_nf_pre_routing+0x5b8/0x670 [bridge]
[37805.737815]  [<ffffffff8159c3a4>] nf_iterate+0x84/0xb0
[37805.737824]  [<ffffffffa04abe70>] ? br_handle_local_finish+0x50/0x50 [bridge]
[37805.737829]  [<ffffffff8159c444>] nf_hook_slow+0x74/0x130
[37805.737837]  [<ffffffffa04abe70>] ? br_handle_local_finish+0x50/0x50 [bridge]
[37805.737847]  [<ffffffffa04ac2c8>] br_handle_frame+0x1c8/0x260 [bridge]
[37805.737853]  [<ffffffff81681c6a>] ? common_interrupt+0x6a/0x6a
[37805.737861]  [<ffffffffa04ac100>] ? br_handle_frame_finish+0x290/0x290 [bridge]
[37805.737868]  [<ffffffff81570caa>] __netif_receive_skb+0x43a/0x620
[37805.737873]  [<ffffffff81571053>] netif_receive_skb+0x23/0x90
[37805.737878]  [<ffffffff815714ac>] ? dev_gro_receive+0x1ac/0x290
[37805.737883]  [<ffffffff815711f0>] napi_skb_finish+0x70/0xa0
[37805.737888]  [<ffffffff81571895>] napi_gro_receive+0xf5/0x130
[37805.737923]  [<ffffffffa00534cb>] rtl8169_poll+0x18b/0x6e0 [r8169]
[37805.737928]  [<ffffffff81571ac3>] net_rx_action+0x123/0x220
[37805.737934]  [<ffffffff8105a726>] __do_softirq+0xb6/0x1d0
[37805.737940]  [<ffffffff816817de>] ? _raw_spin_lock+0xe/0x20
[37805.737945]  [<ffffffff8168ae5c>] call_softirq+0x1c/0x30
[37805.737950]  [<ffffffff81015115>] do_softirq+0x75/0xb0
[37805.737955]  [<ffffffff8105aaf5>] irq_exit+0xa5/0xb0
[37805.737960]  [<ffffffff8168b6d3>] do_IRQ+0x63/0xe0
[37805.737965]  [<ffffffff81681c6a>] common_interrupt+0x6a/0x6a
[37805.737968]  <EOI>  [<ffffffffa02c0339>] ? vcpu_enter_guest+0x479/0xa10 [kvm]
[37805.738026]  [<ffffffffa02c0327>] ? vcpu_enter_guest+0x467/0xa10 [kvm]
[37805.738049]  [<ffffffffa02c0fc8>] kvm_arch_vcpu_ioctl_run+0x318/0x5a0 [kvm]
[37805.738068]  [<ffffffffa02a983a>] kvm_vcpu_ioctl+0x3ea/0x610 [kvm]
[37805.738075]  [<ffffffff810ad721>] ? do_futex+0x101/0xa60
[37805.738081]  [<ffffffff81194349>] do_vfs_ioctl+0x99/0x590
[37805.738087]  [<ffffffff810ad621>] ? do_futex+0x1/0xa60
[37805.738092]  [<ffffffff810ae10d>] ? sys_futex+0x8d/0x190
[37805.738096]  [<ffffffff811948d9>] sys_ioctl+0x99/0xa0
[37805.738103]  [<ffffffff81689a69>] system_call_fastpath+0x16/0x1b
[37805.738106] handlers:
[37805.739705] [<ffffffff814b0940>] usb_hcd_irq
[37805.741326] [<ffffffffa00840a0>] irq_handler [firewire_ohci]
[37805.742928] Disabling IRQ #16