The second problem with the capturing of player characters is the sense of lack of control. In fact, this is one of those areas where story-based RP can go very awry. Players like to know that their actions have real consequences—that they have a say in how the story goes. To present them with an 'inescapable capture' is to take away that control and may throw them a bit out of character, as if they are just watching the story, not participating in it.
The third problem is related to both of the above. Simply put—players will do every freaking thing they can to win. Or at least that's how it is with most of my characters. This makes capturing them VERY difficult, especially if they're experienced. A small group of 'high-level' PCs is, as any GM knows, a very dangerous thing. Taking them down is a tall task for any group of NPCs. In fact, the escalation of firepower necessary to do the job can be dangerous in and of itself—either in the risk of possibly KILLING the PCs or in the risk of making the players feel as though they were 'cheated' by the GM.
And finally, there is the matter of the gear-centric PC. They don't want to be captured because they're afraid of losing their favorite blaster or armor or lightsaber. This, again, is an understandable thing.
So, what is the solution to all of this? Well, the most simple is—try NOT to force your PCs into getting captured. At least not without a fighting chance to escape it. Yes, you can challenge them, face them with some very difficult opposition. You can trick them into a situation where they will be disadvantaged. But at that point, you should let the battle play out how it will and let the decisions and dice settle the matter. That way, if the players DO lose, they should know that the situation was at least partly their doing—that they lost 'fair and square' rather than being railroaded into something. For the GM trying to use a written adventure, this approach means that you're going to have to come up with alternate paths for any scene where the PCs are 'supposed' to be captured.
Another solution would be to have the capture happen 'off-screen'. The adventure Starfall is a prime example of this. The PCs begin in the brig of a Star Destroyer and have to go from there. Their capture is 'glossed over' in the introduction—thus, the players know at least that this part of the adventure is predestined. They can get over it and move on.
And finally, the solution I favor the most is to establish a gaming 'contract' with your players. This isn't anything formal, but rather just an understanding between you and them—to let them know that if you DO put them in a no-win situation at one point you're going to later give them a chance to get out of it. With new groups or with groups used to sandbox-style play this may take a bit of doing. They may well think that capture equates to instant player kill. With a new group, it may be a good idea to set guidelines for such things down at the very beginning of a campaign, letting them know where you stand on this and other issues. Folded in with this is the idea that even if captured and stripped of their gear, they will have a reasonable chance of getting that gear back (or at the very least of getting something similar).
It may also help to give players some kind of in-game clue to know that the situation they're in is unwinnable (for the moment). A good example of this is Han, Leia and Chewbacca's capture in Empire Strikes back. They walk into a room to find Darth Vader and Boba Fett across from them—and dozens of stormtroopers behind. That kind of quick presentation of overwhelming force is a better idea than slowly escalating a situation and giving the players the impression that they can fight their way out. Still, this isn't an easy thing to gauge. There are times when players are going to resist no matter HOW many enemies you throw at them. That's why you should always try to have a 'Plan B'.
It may also be wise to point out that getting captured is actually a big part of the Star Wars movie mythos. Leia is captured in the Episode IV. Han, Leia and Chewie are captured in Episode V. And almost everyone is imprisoned by Jabba in the last movie. Even the prequels have their fair share of captures—Padme in Episode I (briefly). Padme, Anakin and Obi-Wan in Episode II. Try to convey this concept to your players (preferably a long while before springing an actual capture on them).
Anyway, this is just a helpful hint from a guy who's had some really great PC captures and a couple really rough ones. Good gaming!