Beef Wellington - how to get it (especially the pastry) right?
I don't know your exact prep but the best thing you could do is bring your dough to a completely thawed state, store bought will work fine. 
Make sure you beef is at room temperature before doing a quick sear, this will not only add flavor but will give you a layer of protection.
Another problem that can occur is the puff pastry releases some steam and it needs some way to escape. After you have wrapped your piece of meat, take a knife and make small slits in it with the tip of a sharp knife. This will help release the steam and should take away the moisture.
425 degrees would be a good temperature to cook at and you should hit your ideal around 40 to 45 minutes.
Hope this helps and let me know how to it turns out.