If you've been upgrading OSX for a while, you may have some kernel extensions lying around that are no longer compatible, and may have been installed long enough ago that the uninstallers don't work.
When upgrading from Mountain Lion to Mavericks I noticed MacFuse 2.1.7 which stopped development back in 2009. There's a 2.1.9 that works on Lion and a 2.2.0, but the project has been superseded by OSXFUSE which is on 2.6.0 as of this writing, available at http://osxfuse.github.io.
In the meantime, you need to uninstall MacFuse. If you click the uninstall button in the 32-bit preference pane, nothing happens. If you track down the original fuse.fs package, it's in /Library/Filesystems/fuse.fs, but the uninstall script errors out with the message:
MacFUSE Uninstaller: Can not find the Archive.bom for MacFUSE Core package.
Several blogs suggest you simply need to add newer OSX version numbers to fix this. That's true if your MacFuse bill of materials (bom) file is where the script thinks, at /var/db/receipts/com.google.macfuse.core.bom, but mine wasn't. Mine was at /Library/Receipts/boms/com.google.macfuse.core.bom.
To fix this, edit the script:
find the section that tests your OSX version (search for uname), and update it:
Of course, use whatever path really has your com.googlemacfuse.core.bom file.
Save, run the revised script, and two pages worth of files are removed. Finally, you need to remove the MacFuse System Preferences pane.
Right click it, and choose Remove "MacFuse" Preference Pane.
Now go get OSXFUSE and enjoy.