This is with a 64-bit OpenSolaris? host (2009.06). It happens with all tested guests (XP, Ubuntu, OpenSolaris?, Solaris 10), both with NAT and bridged networking. The problem did not exist prior to 3.0.0, and has been confirmed both with pre-existing guests and newly created guests.
When you open an FTP session from the guest to the OpenSolaris? host, the host returns an error like this one from a NAT guest:
Jun 21 19:50:21 fnog ftpd[1902]: [ID 227848 daemon.warning] refused PORT 10.0.2.15,60783 from fnog [192.168.99.22]
192.168.99.22 is the host IP.
If you do the same with VB 2.2.4 on the same host, ftpd logs no errors and successfully connects the guest. This has been tested on two different hosts. Both tested installations of the host OS use an unmodified default ftp configuration.
With FTP servers on the Internet, VB guests connect, but are unable to list files or directories on the FTP server using either the 'ls' or 'dir' commands. The same FTP servers interact normally with computers that are not VB guests. One tested example would be ftp.sunfreeware.com.
Shared folders and SSH/SCP/SFTP exhibit no observed problems from guest to host, but are slower for large transfers and for network testing.
I will be attaching a log file soon.