I have been using bootcamp to partition my iMac for over a year. Sometimes it has needed a couple of attempts to bring up the two disc symbols of the partitions. Now when I reboot, either a white screen comes up and stays there til I reboot again or the standard Apple logo appears and Mac boots up. I haven't been able to access the Windows partition for several weeks.
iMac (27-inch Late 2009), Mac OS X (10.6.8), I use bootcamp