I have a slide phone (Nokia 6110 nav) and it went for a breif swim on my birthday... Into a cup of rum.
the next day it would not slide, well it would, but it took a lot of effort. So smart ol' me thought it would be a good idea to give the rails a quick spit of WD40. It slides better than ever now! Although I did use a bit too much and it's seeped it's way under the screen and have left a dark stain! It's shrinking, slowly. I've got to know it as my WD40 indicator, once the stain has gone, it's time for more!