Machine stops responding for a minute or so?

[jse at xmission.com]

I have a remote machine running icecast to send an internet radio stream 
and it also serves the web page.  Every now and then it just quits 
responding for a minute or so.  The audio stream stops, it won't dish up 
the web page, I can't ping it, and the ssh session I keep open doesn't 
respond either. 
 
There is a Linux router on the network connection and it still responds 
during the bad period so I don't believe it is an external network 
problem. 
 
This morning when it happened as soon as I could get back in I looked at 
the log files and the only thing that looked unusual was about the time it 
stopped responding there was this entry in http-access.log: 
 
209.42.72.248 - - [20/Sep/2003:08:28:21 -0600] "GET /scripts/nsiislog.dll" 
404 - "-" "-" 
 
which I assume was someone looking for a vulnerable IIS server?  That 
shouldn't cause any grief should it? 
 
Does anybody have any ideas why it would just go away like that?  And is 
there anything I could look for? 
 
Thanks 
  -Scott