Hi Delight,
I would have thought that the recent news on how computers are linked to mental health issues (in children, causes of depression in adults, impact on social relationships) would be a good starting point for a relevant and timely topic?!?! A qualitative study on the forum or blog responses to these news articles would be interesting from a sociological point of view. Findings could help better understand how the general public feel about computers and mental health and the study would be feasible to conduct. It may also make you an appealing employee in the future as this is likely to be a topic that the whole of the health and computer industry will have to be interested in - I will say though that this is not my personal area of knowledge and so you may have already dismissed this!
Good luck and enjoy whatever you chose,
Kate