On new Linux installation I tried on a less than a year old machine with a serial port,
on boot it stuck with this message
serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
I bypassed it with
this solution by
putting acpi=off (and not pnpacpi=off)
on the kernel parameters in /boot/grub/grub.cfg
menuentry 'Linux Mint 11, 2.6.38-8-generic (/dev/sda5)' --class linuxmint --class gnu-linux --class gnu --class os { recordfail set gfxpayload=$linux_gfx_mode insmod part_msdos insmod ext2 set root='(/dev/sda,msdos5)' search --no-floppy --fs-uuid --set=root 0ba1e79f-6fe8-4c93-ad65-9c1c778ce4ff linux /boot/vmlinuz-2.6.38-8-generic root=UUID=0ba1e79f-6fe8-4c93-ad65-9c1c778ce4ff ro quiet splash vt.handoff=7 acpi=off initrd /boot/initrd.img-2.6.38-8-generic}Only problem now is that you have to close the PC by pressing the power off button after you shutdown in linux mint 11.
UPDATE:better pass the parameter irqpoll to the kernel
sudo gedit /etc/default/grub
Modify next line
GRUB_CMDLINE_LINUX_DEFAULT="irqpoll"
sudo update-grub