How technical do you want to get with this?
I have a couple of interesting ideas off the top of my head, but not sure how deep you can/want to go here ... is there a course syllabi to see? Or is it kind of open? Also not sure what you are looking for in terms of a project, do you want to engineer something or do you want to work out things like workflow or process using existing stuff?
Gerk, it would have to be something that is achievable in 4 months, I guess a typical structure would be to state a goal, form a set of requirements, analyse the problem, design and implement it, test it and make conclusions. I imagine an audio fingerprinting algorithm for detection of copyright violation would have been a great example of the kind of thing... e.g. how to recognise a song with a good degree of accuracy, what criteria to use, how to compare with a database for comparison, field testing in an environment like YouTube....
I'm going over to the university today to see if there's anyone there who can give me a few ideas too.
Cheers
Mike