IE7 Beta and VWD Style Builder.
There's a bug in the IE7 beta which seems to break the style builder. Of course we'll work on getting it fixed but in the meantime, if you happen to have IE7 installed, there's a workaround you can apply.
Create a new DWORD reg-key named "devenv.exe" with the value "0" at the following location:
Read more about it here: http://blogs.msdn.com/petel