wubi dial boot problem

windows 7 starter netbook was set up to dual boot into Ubuntu 10.4 with Wubie install. It worked fine until my last update install
I can no longer boot into Ubuntu sector. I tried using repair boot, which has worked in the past, but no joy. BTW Boot files for Ubuntu are on a 16 gig SD card.
Any ideas on how to recover data form sector or repair the boot.