ok, i ran the online updater, and it went all fine, and it installed a newer version of the kernel. i restart, and when i select "Linux" in grub, it comes up with an error saying that its not in a correct sector. HELP ME! please?

Although system update tools often allow it, it seems that one should not update the kernel VIA an update tool. Find the instructions to do it manually and confirm you have a secondary method to boot your system, boot floppy or CD, before updating.
Hopefully you can boot from the boot floppy you made after install and follow these correct instructions to install the new kernel package.
http://www.suse.de/de/security/2004_...ux_kernel.html

YaST also messed up my computer--my nVidia network card didn't work after installing the new drivers from online. I tried to un-install the package, and now X won't start (the driver package had everything: video, sound, LAN) because the update replaced the working LAN drivers that I installed manually, so I tried removing it.

unfortunatly, i have made no rescue floppy. what are some alternatives? are there any good rescue cd ISOs out there? the EXECT error was "Error 18: Selected cylinder exceeds maximum supported by BIOS"

Is my only option to format?

It may not be your only option, but you may consider it the easiest.
Since I installed my Suse 9 VIA FTP, I only have an FTP Download Boot CD. That has a rescue option. If I select the rescue option I can mount my Suse partition then "chroot" ("chroot /mnt/name_of_mnt_point") to it. If you are familar with console mode you could poke around and perhaps reinstall the bootloader or run the correct "RPM" command for the kernel.
I don't know what is in the commercial CDs if that is what you have. The install CD probably also has a rescue system. I could not find an option like Slackware has to boot an installed system with the "root=/dev/hdaX" command.
1. It is possible you just need to reinstall the bootloader. (I can't help you with Grub.)
2. You may need to reinstall the kernel package. That would mean either finding it on your system or redownloading it.
3. You may decide reinstalling is easier.
Partially your call....

EDIT: I am a newbie, just posted on the wrong thread! Don't know how.
Before I registered I was on a SUSE10.3 thread.

I just did the same, used the online update. Kernel updated, but now I have a few fails. I can't use my wireless for one thing.

Does anyone know how to revert to the previous Kernel?