i have had the same problem recently,i used a wallpaper scraper and made up a solution using 3 tablespoons of sugar soap,4 tablespoons of soda crystals and 5 tablespoons of vinegar with 500ml water just mix it all together and apply with a cloth or sponge,start scraping straight away as it dries in very quickly,dont forget to wear rubber gloves to protect your hands.
beth, April 2008