Het schijnt dat versatel met een update alle beveiligingsmogelijkheden heeft weggenomen:
if only vers*tel had not deactivated nearly all of its configuration options, the davolink modem would not only support WPA PSK, but also the newer WPA2 and PSK2.
(You can *still* see that if you read throug the html-source of the security page [right click, open frame in new window])
Until the last modem update there was a possibility to activate this features anyway, but that is gone now. i definitely had PSK2 up and running for several days, thus i know the modem can support it.
By now, the only WPA option left is WPA with a radius key server, which is rather useless in home environments.
You'd need to setup an - always online - radius server in your intranet or better use one in the internet, but who has access to such features??
I fully understand, that the modem remains versatels property and they may configure it anyway they want. Maybe there are technical reasons -unknown to me- that encouraged them to deactivate these configuration options.
From a users point of view this policy is only annoying and if you focus on security its unacceptable, since they place a piece of equipment in your private net, which is by default unsecure and not fully under your control.
Back to the question:
if you really want / need WPA, you should deactivate the whole wireless part of versatels modem and connect a WPA2/PSK2 wireless router to one of the lan ports. That will also overcome the security problem due to vers*tels access to your private network, if you set it up properly.
if you are less paranoid, i would suggest to use WEP (128) encryption in conjunction with the MAC Filter Option.
[note: this is no cure against attempts to decrypt your WEP key, but you can give away the key to all allowed users and still control which wireless clients may access your net]