You can read about it all on their web-site:
http://www.goldenstate.com.au/news.shtml
Was driven up on their nickel assets and perhaps on notice that they had signed an agreement (were about to) with a software company (resource mapping I do believe). Remember this was at the peak of the dot-com bubble and the drop coincides to some degree with the crash (maybe a couple of weeks out).
Cheers
SBC