We have 64-bit version but it is not public yet. Which WS version are
you using?
WS 0.8 has a few problems that we already know of but due to
practicalities we wont fix. 0.9 is a massive improvement over 0.8 so
you should see a lot less issues. At the moment you can download
Websecurify 0.9Beta1 from here:
http://code.google.com/p/websecurify/downloads/list.
You may still experience some issues because this release doesn't have
an important patch which we've landed yesterday.
Let me know if this helps.