5.2RC1 / Dell Dimension 2400 / Repeatable ACPI problems

Hi,

Having just installed 5.2-RC1 on a new Dell Dimension 2400 (mainly for the
Broadcom 440x BFE driver) I was testing out ACPI support:

acpiconf -s {4,5} causes a hard reboot
acpiconf -s 3 renders the machine unbootable until after I reset the CMOS
via a jumper on the motherboard.

Is anyone interested in data about this problem?  I believe the BIOS is
Phoenix 1.01 A03 (not sure about that string), and I'm willing to figure
out the kernel debugger (or whatever else is necessary) if someone can
tell me what sort of issues I'm looking for.

Best Regards,
Mark