Did you install an application, or make changes to any system files during this time? Linux is pretty easy to fix when things like this happen, but in most cases, for a new user, it's usually easier to try a reinstall. (Gotta wash my mouth out with soap after saying that!) If you had a little experience with Linux and/or the command line, it would be fairly easy for someone to talk you through the problem, but doing so with new users tends to turn them off to Linux. On the other hand, if you've got the patience of a god, and the geeky curiousity that it requires to start from nothing and fix your system, you can fix it, probably pretty easily. (Well, in retrospect, it will seem easy.)
However, like I said, it would likely just make you think Linux is harder to use than it is, and seeing as Linux is a lot faster to reinstall (and repair) than most other OSs, at your experience level, I think it's probably better for you to reinstall it, and get familiar with the OS before you have to jump into a mess of new, confusing information. Though, for what it's worth, if you have a CD burner (or a friend with one), you might want to consider a slightly newer distribution, as RH9 is a little on the crusty side, and the newer ones are much easier to install and far more user friendly. Fedora (Redhat's version after RH9) is decent, but for brand new users, I still like Mandrake, and you can download it free, too.
If you can't do that, RH9 is fine, but I'd reinstall it. If you have something important on the broken system, find someone with a Knoppix CD (again, you can download and burn it free as well), and you should be able to boot to the cd drive with the knoppix disk in, and pull anything important off your broken system.
Now for the dangerous part, and this is guaranteed not to work 99% of the time for newbies. You said you logged in, and then you have the problem. Assuming that you are logging in from a gui (mouse-using system), you might be able to use the login manager, but the specific user stuff is somehow messed up. Hit <ctrl-alt-F1> and you should go to the command line (DOS looking thing). Assuming you did a standard install, you might be able to log in, and type 'startx' at the command prompt. This may work, probably not. If not, hit <ctrl-alt-backspace> and you should dump out to command line again. If not, hit <ctrl-alt-F1> and when the command line pops up, <ctrl-c>. That should stop what was running. Alternatively, you could go into another console by hitting <alt-F2> or alt and any F-key from 1-6, and receive a command line/login. Once you get one, you might want to try typing 'kdm', if you have kde installed, and that might work as well.
As you can see, there are tons of ways to approach problems in Linux, which is really nice for users with a little experience. Obviously, I didn't give you a thorough explaination of the myriad of ways to solve your problem because they would likely overwhelm you at this point, but I hope it also encourages you, in the sense that once you spend a little bit of time getting to know Linux (and it's cumulative, unlike most OSs--what is the point of a registry fix in MS Windows, when you don't have a clue what the heck the fix actually does?!!), you can fix Linux even when it seems nearly impossible.
Here's the skinny on your situation, which I forgot during my rambling. There is a problem with your X-Windows setup (typically, the config files for X-Windows are in /etc/X11/ or something similar). Either your resolution is wrong, or the drivers for your video card are set up wrong, or maybe even the wrong mouse or keyboard setting (for some dumb reason, X-Windows wrote the configuration file for wheel/scroll-mice incorrectly, though if yours worked before, there's no good reason it shouldn't now, unless you ran an update that screwed things up, which is likely if you allowed it to use default settings if it asked during the update.)
The sad part is, your system is fine, just one little peice of it is incorrectly configured. The worst part is, if you had a little more experience with Linux, you could fix it. However, like I said before, a detailed explaination would likely make you think it was a bigger problem than it really is. Don't worry though, we've all been there, though on the upside, less of us have been there recently than in the time when I started.