This may sound like a silly question, but I'm currently working on a solution on pc for a client on mac. I'm going to create a runtime version for him. Is there anything special I need to do to accomodate the mac?

Mac runtimes will have to be created on a Mac and Windows runtimes will have to be created on a Win, although the actual files to create the runtimes can be the same set.

It is also best to test layouts on a Mac too, as font differences can mean that layouts break - text wrapping etc.

I use it on Mac, to make most of the solution, then fire up Virtual PC to tweak the PC application before building it on PC. There are usually layout changes to be made.