There are a couple other variables you did not mention like the MAC fs your running. but either way this is how I overcame that same issue but in VMWare and I had a MAC OS X connection off the host, but on the same internal network. I have always noticed that when connecting remotely with MAC machines the security settings are always a problem even when backing up files en-mass I have had "permission" problems.
For the MAC connections I always install Samba on the Linux guest and then configure it to allow the specific parameters for the MAC's on my network (I mean Apple MAC's not MAC addr) and I make sure to disable all authorization / passwords for those shares and machines. Then from the MAC I make the connection to the Samba share. That way I am connecting in the other direction from the MAC and I am using Samba to manage the connection on the guest, the files I share between the two are never a problem in this config.
I know Vbox and VMWare both provide tools so you don't have to do this and they usually always work well. But Apple is always the challenge when connecting outside the Apple proper and it usually comes down to the MAC fs.
Give Samba a try it's pretty easy and makes ocnnecting to Linux very easy no matter the fs or connection.