recently started crashing 4 am

    Anyone know what be causing what appears to be something in cron (4 am or 
so) freezing the machine - started happening the last week or so after some 
bout of updates - including kde 3.5.8.

     After kde update I had to diable knetwork manager which made the machine 
interminably slow for user to login - removing it fixed that problem - nm is 
not runnning.

       Now it is freezing around 4 am .. any ideas what may be causing this ? 
Its been a happy F7 machine for a long time prior to this ?

      I could not find any interesting info in log files. Box is not visible 
to internet either.

      Thanks for any pointers ... 

gene