Help with windows server!!!

[Hades]

What is wrong my server restarts automatically every few hours i found this resyart log in windows log:

No title for this reason could be found
      
      winlogon.exe
      
      2005-9-10
      
      0-55-38 (Pacific Standard Time(480))
      
      0x50006
      
      restart
      
      The system process 'C:\WINDOWS\system32\lsass.exe' terminated unexpectedly with status code 128.  The system will now shut down and restart.
      
        0  3:38:37.453
      
      0x0409
      
      0x0409
      
      1.0
      
   
   
      
         \??\C:\pagefile.sys
         
         774144
         
         12684
         
         17880
         
      
   
   
      
         515572
         
         307388
         
      
      228876
      
      
         206072
         
         162280
         
         1264384
         
         225884


There is more but i think this should tell the reason - what could be done to fix it?