If I mount an smb share on a windows 98se (no chance to test the others),
and if I don't un mount it before rebooting, the boot process halts at the
unmounting filesystems stage. I must admit I did not wait long to see if it
would continue, but I did have this exact problem on a server at work a few
months ago. At that point I had no choice but to pull the plug to reboot
it, as it was a headless server.
smbmount //scooby/c /home/dan/smbscooby -U guest
Did you have the netfs 'service' running? This will unmount
smb filesystems on shutdown.
When initscripts-5.04 is released, it should automatically
run 'netfs stop' on network stoppage if needed.