tl;dr:
try to manually update fuse4x-kect after updating the ports' tree using sync verb
port sync
port upgrade fuse4x-kext
Longer read
The error you pasted means that somehow macports didn't update the kext port fuse4x-kext when it upgraded fuse4x, it should have. I doubt your issue is still actual, since you're likely to have updated since october 2012, you should perform regular ports' upgrades and check when a new macports version is out in order to run a selfupdate verb.
As future reference you can guess what the kext port for a port is by looking at its information
port info fuse4x
or list of dependencies:
port deps fuse4x
Ports offering kexts can be loaded and unloaded from kernel by using load and unload verb.