It is a problem, the pins get gunged up very easily. Put aside a morning and take 'em apart give 'em a good old clean and regrease the pins, use the proper grease, get some from your dealer)
When mine were binding when I first got the bike it cost me over £100 for the dealer to sort it. It really it the easiest job in the world to do yourself (*if* the pins aren't already stuck!) I gave mine a pukka clean up when I replaced the pads... *should* get me through winter
Also see the FAQ on the main site...
Good luck