As above when I open the lid of my mac the screen just stays blank rather than asking for my log in. I have to switch it off and on again to get logged on . I has just started doing this in the past few days nothing has been changed. Any mac users have any suggestions.

did you update to 10.8.2 recently, mine wakes from sleep but seems to do it in a slightly delayed fashion while trying to spin the drive for some reason, there area bunch of posts on various forums about it.

thank for that I did update recently will search mac forums