Just like you, valve stem issues, usually after pumping up the tube I am "deflated" by either a rupture , breaking the valve stem off or breaking the core when unscrewing/screwing it. I started 2007 with a new personal record of 3 in a row and 2 disabled bikes before I got one that co-operated. I don't swear tho, just start mumbling & talking to myself about the injustices of life. Don