Can you tell me what kind of computer you are using?
If you are using a laptop or something, I could give you some help with that:
at the bootmenu, go to the entry that boots into the 2.6 kernel and type 'e' If I'm correct, you should be seeing the commands that the bootloader uses to boot your Debian. Under commands or something similar, I forgot, edit it, adding:
acpi=off pnpbios=off noapic noapm
Once again, some more information about your computer would help.