Please note that as of June 23 2007
the coordinates of the cache have changed. If you have already
solved the mystery before this date, you can simply use the same
method to obtain the new coordinates.
The cache is hidden at: abcdefghijk
At coordinate N 51 11.147 E 06 08.185 you'll find the
hint.
In case you need the hint, it might be slick to have someone
behind a computer to solve the problem.