2.5.74: ALSA lockups, and ACPI, IRQ routing

As I've reported several times to LKML, I'm experiencing annoying ALSA lockups when using multimedia programs like xmms, xine, and mplayer.
My problem wasn't fixed in the last 4-5 kernels or so but I managed to figure out a workaround. When booting with acpi=off, the lockups are gone.

Why?
Here's some info....
==========================================
ALSA errors with DEBUG on memory allocation, and verbose prink:

ALSA sound/core/pcm_lib.c:215: Unexpected hw_pointer value (stream = 0, delta:
-6488, max jitter = 8192): wrong interrupt acknowledge?
ALSA sound/pci/via82xx.c:687: invalid via82xx_cur_ptr, using last valid pointe

ALSA sound/core/pcm_native.c:1263: playback drain error (DMA or IRQ trouble?) ALSA sound/pci/via82xx.c:687: invalid via82xx_cur_ptr, using last valid pointer

mplayer:
ALSA lib pcm_hw.c:524:(snd_pcm_hw_drain) SNDRV_PCM_IOCTL_DRAIN failed:
Input/output error
alsa-pause: pcm drain error: Input/output error

========================================
IRQ related ACPI messages/errors:

ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT]
ACPI: PCI Interrupt Link [LNKA] (IRQs 1 3 4 5 6 *7 10 11 12 14 15)
ACPI: PCI Interrupt Link [LNKB] (IRQs 1 *3 4 5 6 7 10 11 12 14 15)
ACPI: PCI Interrupt Link [LNKC] (IRQs 1 3 4 5 6 7 10 *11 12 14 15)
ACPI: PCI Interrupt Link [LNKD] (IRQs 1 3 4 5 6 7 *10 11 12 14 15)
ACPI: PCI Interrupt Link [ALKA] (IRQs 20, disabled)
ACPI: PCI Interrupt Link [ALKB] (IRQs 21, disabled)
ACPI: PCI Interrupt Link [ALKC] (IRQs 22, disabled)
ACPI: PCI Interrupt Link [ALKD] (IRQs 23, disabled)

ACPI: No IRQ known for interrupt pin A of device 0000:00:10.0
ACPI: No IRQ known for interrupt pin B of device 0000:00:10.1
ACPI: No IRQ known for interrupt pin C of device 0000:00:10.2
ACPI: No IRQ known for interrupt pin D of device 0000:00:10.3
ACPI: No IRQ known for interrupt pin A of device 0000:00:11.1 - using IRQ 255
ACPI: No IRQ known for interrupt pin C of device 0000:00:11.5

0000:00:11.5 is my sound device (VIA 8233)

=======================================
/proc/interrupts under 2.5.74 with ACPI (init level 5):
CPU0

  0:     183866    IO-APIC-edge  timer
  1:        336    IO-APIC-edge  i8042
  2:          0          XT-PIC  cascade
  3:          0    IO-APIC-edge  uhci-hcd
  7:          0    IO-APIC-edge  uhci-hcd
  8:          1    IO-APIC-edge  rtc
  9:          0   IO-APIC-level  acpi
 10:          0    IO-APIC-edge  ehci_hcd
 11:          0    IO-APIC-edge  uhci-hcd, VIA8233
 12:       3433    IO-APIC-edge  i8042
 14:      17003    IO-APIC-edge  ide0
 15:         10    IO-APIC-edge  ide1
 16:       8167   IO-APIC-level  nvidia
 18:         32   IO-APIC-level  eth1
 19:        723   IO-APIC-level  eth0
NMI:          0 
LOC:     183783 
ERR:          0
MIS:          0

/proc/interrupts under 2.5.74 with ACPI off (init level 3):
CPU0

  0:      70300    IO-APIC-edge  timer
  1:        516    IO-APIC-edge  i8042
  2:          0          XT-PIC  cascade
  8:       5419    IO-APIC-edge  rtc
 12:        232    IO-APIC-edge  i8042
 14:       2266    IO-APIC-edge  ide0
 15:         10    IO-APIC-edge  ide1
 19:          0   IO-APIC-level  ehci_hcd
 21:          0   IO-APIC-level  uhci-hcd, uhci-hcd, uhci-hcd
 22:        172   IO-APIC-level  VIA8233
NMI:          0 
LOC:      70219 
ERR:          0
MIS:          0

Why does using ACPI cause my soundcard to lockup?
Any help will be greatly appreciated.
(BTW 2.4 kernels worked fine with ACPI on...)