panic: bad stray interrupt | No usable event timer found!

Hi,

When booting an Acer Aspire 2920 I am getting panics with a recent kernel 
(2010/07/28).  The kernel boots successfully from cvsup 
date=2010.06.20.00.00.00.  

The kernel panics with:

uhci0: <Intel 82801H (ICH8) USB controller USB-D> port 0x1820-0x183f irq 20 at 
device 26.0 on pci0
panic: bad stray interrupt
cpuid = 0
<snip/>
db> bt
Trading pid 0 tid 10000
kdb_enter()
intr_event_handle()
intr_execute_handler()
Xapic_isr1()
--- interrupt, rip = 0xffffffff807d904e, rsp = 0xffffffff8108c5e0, rbp = 
0xffffffff8108c680 ---
uma_zalloc_arg()
malloc()
intr_event_add_handler()
intr_add_handler()
pci_setup_intr()
bus_setup_intr()
uhci_pci_attach()
device_attach()
bus_generic_attach()
acpi_pci_attach()
device_attach()
bus_generic_attach()
acpi_pcib_attach()
acpi_pcib_acpi_attach()
device_attach()
bus_generic_attach()
acpi_attach()
device_attach()
bus_generic_attach()
nexus_acpi_attach()
device_attach()
bus_generic_new_pass()
bus_set_pass()
configure()
mi_startup()
btext()

If the kernel is booted in safe mode:

Timecounter "TSC" frequency 2194547740 Hz quality 800
panic: No usable event timer found!
cpuid = 0
<snip/>
db> bt
Tracing pid 0 tid 10000
kdb_enter()
panic()
cpu_initclocks_bsp()
initclocks()
mi_startup()
btext()

Regards,

David