Sometimes the players are missing something that the DM thinks its obvious.
I used to do this in the past, but I actually enjoy being wrong as often as not now. (Not that going with the group's current preference isn't another satisfying style or anything) What I've found is sticking to a single (yet dynamic) situation can help with focus and get people concentrating on what's happening as well as what did and what might happen. Of course it can mean the PCs going off in all sorts of directions where what they expected is not at all what occurs, so this isn't for everyone.And, y'know what else works? When the players have an idea that's wrong, but doesn't contradict anything that's happened in the campaign, it suddenly becomes true. Why? Because that's a lot more fun.
But it's worth pointing out that a game can only stall in this manner if you've already decided where it absolutely has to go and precisely how it's going to get there.
That's not entirely true. In real life or in the game, when you're staring at a dead end and don't know what to do, indecision can be a problem. This goes double if you're used to playing railroads.
And, y'know what else works? When the players have an idea that's wrong, but doesn't contradict anything that's happened in the campaign, it suddenly becomes true. Why? Because that's a lot more fun.
I'm telling. Please PM me their email addresses so I can alert them to this thread.The players really felt (not knowing that I had taken their plot) that they had achieved something which was cool.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.