I was having problems with this, too, and eventually decided on Samba shares. This is probably a stupid question, but did you install the "VirtualBox Guest Additions" thingy in the guest? None of those guides mention installing the guest additions, so I have to ask.
If not, try putting this .iso in the virtual cd-rom drive for your guest machine (this is where it is for me - 1.5.6, installed from the official rpm):
Then mount it to a mount point of your choosing in the guest. I think there's a *.sh of some sort in there for Linux guests and an .exe for Windows guests.
If you've already done this, not sure...
The other option is Samba shares, I suppose, which I think is more flexible anyway (run a Samba server on your host and then just mount the share in the guest as if it's remote using mount -t cifs blah blah).
"What is freedom? To have the will to be responsible for one's self." - Stirner
Last edited by forkbomb; 29th February 2008 at 04:23 PM.