Shouldn't really be helping a competitor I guess, but I'm a nice guy!

I've read a lot of posts where the culprit for problems has been time. I would
seriously suggest implementing support of this
http://www.ntp.org/ into your client and use it to syncronize an internal clock withing the client on start to UTC. You can get a Java API for it and do it all behind the scenes without needing users to piss about with clocks.
You're welcome

I disagree. A workaround like this will only lead to problems later in development. Do you ever show this "internal true time" to the user, e.g. in transaction timestamps? Or do you always compensate for the difference in user-visible fields? This will complicate the code and create obscure bugs, and right now developer's time is our most precious resource. Really, at this early stage users who can't get their computer clocks in sync should not be running Nxt nodes. And development efforts are better directed towards making sure the network is resilient to some node clocks being out of sync - either ignoring, or somehow accommodating those nodes without disrupting all others.