Well I don’t have any experience with this FTP server, but I somehow exepect this to be a flaw in some configuration file, as FTP supports all kinds of settings to lock clients in a directory, give them read-only rights etc etc…
Did you check the manaul pages of the ftp server (I suppose it comes with those)?
If you really can’t figure it out, you might want to try Webmin. Webmin is a webbased configuration panel of Unix (and this Linux) systems. I don’t know if there’s a module for vsftpd, but it’s worth the try. Otherwhise, just switch to proftpd
Webmin can be downloaded from here for free!