SmartFTP - FTPS error

I have just downloaded SmartFTP client 4.0.1227.0 to try with ftps.

The webserver I am using is IIS 7.5 running on Win Server 2008 - with an SSL cert from Verisign.

I have not been able to get this to work - so I then tried running the SmartFTP client against the 'SmartFTP - FTPS' site - which I assume is for testing / demo purposes (Favourites -> SmartFTP FTPS) - but I get an error for that also:

[17:25:17] SmartFTP v4.0.1227.0
[17:25:17] Resolving host name ""
[17:25:17] Connecting to Port: 21
[17:25:17] Connected to
[17:25:18] 220 SmartFTP Server ready...
[17:25:18] AUTH TLS
[17:25:18] 234 AUTH command ok; starting SSL connection.
[17:25:20] SSL: Error (Error=0x80090308).
[17:25:20] The token supplied to the function is invalid
[17:25:20] Client closed the connection.
[17:25:20] Connect failed. Error=0x80090308
[17:25:20] Waiting to retry (30s)...
[17:25:35] Aborted by user.

how can I get this to work ?

What operating system do you run SmartFTP on?