Hard to tell without the relevant (vsftpd? inetd? syslog?) logs.
I'm away for the next weeks/month from any box, can't detail which one. But most certainly it's a missing file or folder, that is created by the vsftpd init script or the post install (upgrade) script. Try running 'rcvsftpd init' from the command line.
There is a similar bug report for opensshd at
sourceforge bug reports that should be fixed using the same technique, 'rcopensshd init'
Both vsftpd and opensshd post install scripts should call these (the post install scripts can be found at /usr/lib/ipkg/info)
Please keep reporting, perhaps given the above hints someone can help further.
Thanks.