So first forum post on GoG and unfortunately it is a bug.

When I'm playing through this game, right after being embraced you have a talk with Ecaterina then Wilhelm appears. The problem is when I am playing at this point Ecaterina doesn't appear, there is just speech without her in the room. Later she appears but Wilhelm doesn't . Rather than join my coterie he simply isn't there and his voice occasionally appears from thin air to give me advice. I really don't want to go through the game with one party slot empty, does anyone have a solution?

For the record I have tried starting from scratch only to see the same thing, I really don't want to do the silver mine again...

Thanks!

EDIT: Oh yes I forgot to mention. I tried also running it as an administrator and with all settings on minimum. I have a 64 bit Windows 7 system

Also I'd be fine accepting a savegame file right after Wilhelm joins you just to bypass the problem.

Have You tried redownloading and reinstalling the game?

Had same problem, I played through it once, the first time, and got past it, attacked the townsfolk accidently, lost a bunch of humanity, decided to reload, of course there's a bug with vista/seven and save files don't overwrite, so I got sent back to just after the silver mines, when I did it again, time and time again, problem resumes.

apparently reinstalling the game won't hurt because save files are stored in a different place in windows vista, I'll try it and let you know.

Reinstalling didn't help, short of restarting the game and hoping that it works...

I am experiencing the same problem here. It´s ruining the game.

I remember reading somewhere here that if you install the game in a "standard" folder like Program Files or Program Files (x86) then the game has trouble accessing certain files.

What I did was install the game in D:\Games (C:\ being a 64GB partition reserved exclusively for the Windows installation, you could try C:\Games instead) and run the game as an Administrator and have never had the problem.

As for the silvermines, actually it is extremely easy to pass that point in no time using cheats (add the -console handle in the shortcut after the " character and with a space between them.
You calculate how much xp you get until you reach the 3rd level of the silver mines, start a new game, go through the intro, open the console (press the ~ button) and type "jump SilverMines3".
You're sent to the first boss battle, you add the xp you WOULD have gotten if you had played the silver mines using the console command xp xxx (where xxx is the xp, to add) go through the battle and then type "jump SilverMines" to get sent back to the entry. All you have to do then is go back to the town :)