You need to get the permissions correct. Change the owner of all the modules to root, and make sure that you are using the correct kernel and compatible modules. Also, try upgrading your version of modutils to something newer. Go through all that, and you are probably going to fix the problem. I have had the same issue many times.
Oh, and I spelled synthesizer wrong, as synthesiser. But now it is stuck that way, so no Z. It looks better this way anyways...