filezilla server and iis on same server

[lore]

Hi

I have a windows 2000 server and IIS ftp service running on first
ip address.

I want to run filezilla on the same server using two ip aliases

IIS ftp is listening on first ip address x.y.z.a

In FileZilla Server version 0.9.18 beta I specified to bind
on an alias ip address but when i try to star filezilla server
i receive the error:
Failed to bind the listen socket on port 21 to the following IPs: x.y.z.b
Failed to create a listen socket on any of the specified ports. Server is not online!

if I try to connect to x.y.z.a IIS is working on x.y.z.b no reply

Can anyone help me ?

Thank you

[botg]

The address is in use by IIS still it seems.