freebsd 4.x remote server instable...

[Christian Tischler]

Hi,
I take care of an remote 4.x server and everything worked fine for over 
an year, but now the box gets unreachable every now and then, but I have 
no clue why this could be.
My question is what kind of logging facility I could run, I addition to 
the standart out of the box ones, that could tell me what leads to these 
"crashes"?
Sorry for the poor description, but that is all I know, too.

Christian