Problem

Unable to establish an TLS session on Windows Vista to some FTP servers. For example Netware. In this case the log may look like this:
Connected to ftp.host.tld.
220 Service Ready for new User
AUTH TLS
234 Enabling SSL
Connected. Exchanging encryption keys...
An established connection was aborted by the software in your host machine.

or

AUTH TLS
234 AUTH command accepted - proceed with Negotiation.
Connected. Exchanging encryption keys...
SSL/TLS client handshake failed (Error = 0x80090308).
The token supplied to the function is invalid

Reason

By default SSL 2.0 is disabled on Windows Vista for security reasons.

Solution

Enable SSL 2.0 by editing the registry. Set the DisabledByDefault value to 0.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\Schannel\Protocols\SSL 2.0\Client
DisabledByDefault DWORD 0x00000000