just to keep the rpm database current, yeah, you probably should. otherwise you mighte get conflicting version problems later on -
the modutils are mostly a set of daemons and programs that tell the kernel when a certain module is needed. as root, you can run 'lsmod' to see what modules are loaded by your kerenel - there's some conflicts between the 2.2. and the 2.4 kernel - so the old modutils don't work perfectly. the 2.4.x modutils should be backwards compatible if you ever want to go back to the 2.2 kernel.
let us know if you have any other problems - it could still be a vid-card problem or something like that.