Wahay, finally got it working!

Initially couldn't even install the Java update but it turns out that we hadn't updated any software for over a year and we needed further software updates before we could even install the latest Java version.

Simply used the Software Update function in System Preferences and installed all the updates we needed from there. Told you I was a newb!

Once the latest OS X 2 updates were installed, had no problems installing Limewire.

Thanks for all the help guys!