In Fusion (and other virtualization systems) you should install OS tools on the guest OS to make it behave better. This is not something specific to Fusion, this is a general fact of virtualization. Usually, clicking the "Install VMWare Tools" does the trick--especially with Windows. Sometimes, however, it doesn't do anything. On those occasions you need to take over and do it manually. Here's how.
First, mount the right ISO as a CDROM image. You'll find these in
/Library/Application Support/VMWare Fusion/isoimages
Select the right one for your OS. You may need to manually mount the disk. Fedora, for example, should automatically mount the CDROM when you connect it, but sometimes it doesn't. As root, use a command like this one to mount it:
mount /dev/hdc /mnt/media -t iso9660
I say "like this one" because you'll have to figure out which device is the CDROM. Note that if the /mnt/media directory doesn't exist, you may get an error.
The image will contain a tarball. Untar it to a convenient directory and then run the Perl script. It will ask you lots of questions. For Fedora Core , I accepted it's default answers and it worked great. If it can't find the right version of vmmemctl it will try to build it. This worked flawlessly for me. If it doesn't for you, it probably needs include files from packages you didn't load at install. I always load the developer and kernel building packages.
That's it, a reboot or an X restart and you're done.