problem when restart Mac

Hi guys! Ok i Have a huge problem here. I have a 10.4 Tiger and I updated softward onto it today called "backup". Everything was going fine until I had to restart and now when I try to turn it back on everything totally jams at the welcome page. Has anyone got any advice on this as I really really need it!

Thanks

What do you mean by Jam?
How far are you actaully getting?
What do you see? Any messages or text?
Did you "need" to restart because of the "backup" program or for another reason?

You could also try booting from the Install Disc.
Hold the C key down while booting to boot from CD-ROM.
Run Disk Utility to check and repair permissions.