Hi, actually there are a few people on here with Logitech USB mice, and they have gotten them working by editing their /etc/X11/XF86Config-4 file. As long as you have the support compiled into the kernel, and the correct lines in the XF86Config-4 file, then you should be able to use your mouse. I very recently had problems with it, and found that I didn't have USB compiled into my kernel, and that I wasn't calling the USB module before starting X.
Since you cannot even get through a boot, I would try booting the failsafe option. I don't use GRUB, but I would suppose that redhat places that option reguardless of which bootloader you use. Also, if you can do a "interactive" bootup. Press I during the bootup process to do this. Disable checking for new hardware and such, and then hopefully you can get in. Then chang your run level from a 5 to a 3 in your /etc/inittab file using your favorite command line text editor.
If you have never compiled a kernel before, read a few of the thread on here about the process, and possibly check out the LDP's
how to on kernel building.