Interrupt storm detected, today's -current doesn't boot

I am tracking -CURRENT on a Dell Optiplex GX270.  I cvsupped and installed a 
new kernel and world today, and my machine had trouble booting.

Toward the end of the kernel boot messages (and before init is started), I 
get:

Interrupt storm detected on "irq18: em0 uhci2++"; throttling interrupt 
source

The boot does not continue from that point.  It doesn't freeze, since I can 
still scroll back and forth in the buffer with scroll lock, but it stops 
doing anything useful.

I tried disabling usb in the machine's BIOS.  I got the same message, but 
"atapci0+" took the place of "uhci2++".  With ethernet AND usb disabled in 
the BIOS, the message was:

Interrupt storm detected on "irq18: atapci0+"; throttling interrupt source.

I tried booting without ACPI, with no benefit.  I was able to boot in "safe 
mode", however.  The dmesg of that boot is attached.  The important 
difference that safe mode makes is the IRQ's assigned to the devices.  In 
the problematic "normal" boot, just about everything has a high (>15) IRQ, 
whereas in a "safe" boot, all the IRQ's are in the traditional range.

A possibly related tidbit is that the floppy drive is no longer detected 
properly, and it was before today's update.  My last update before today 
was on June 7.

Does anyone know offhand what would be causing this?  What other information 
should I provide?

Thanks,

JN