To load/unload a module, it's better to use modprobe.You also don't need the '.ko'
$ sudo modprobe uvcvideo
$ sudo modprobe -r uvcvideo
Did you just compile a kernel module? If so, you need to copy it the right place, you can't just call it like that. Kernel modules usually goes into /lib/modules/2.6.xx
There's usually a script that will do that for you. If you have run the script, but can't load the module, try running ldconfig or rebooting the system.