I maintain six computers in a school, used by staff. Almost all the time the computers run fast and do their tasks acceptably. But once every week or two the machines become unusable, showing symptoms of significant resource starvation, which I refer to here as "lockup":
1. The machines are in a logged-in state, or have timed out from logged-in via the screen-saver.
2. Ctrl-Alt-Del results in message "The application failed to initialize properly (0xc00000017)."
3. Starting Winword.exe 2003 results in "Not enough quota is available to process this command."
4. Trying to make a new folder on Desktop results in message "Insufficient system resources exist to complete the requested service."
5. Double-clicking on the Time in Systray results in mesasge "Windows cannot find 'C:\Windows\System32\rundll32.exe."
6. Google Desktop says it is not running.
7. GoToMyPC says it is not connected to Internet (though the connection exists physically and is competent)
8. All other actions result in no response (Rt-Click on the taskbar or Desktop, or click on Firefox, My Computer, My Network Places, Start)
9. If I click on the Power button, the system shuts down in an orderly way, unprompted by me. Restart results in normal operation until the next lockup.
10. The computers are all Dell Optiplexes of different ages, up to 3 years. One is brand new.
11. The computers tend to lock up on weekends. I have removed one computer to an outside location but it still locked up after a few days.
12. The symptom 11 (weekend lockup) led me to guess that the lockup is triggered by user inactivity. Evidence: I have been able to prevent one machine from entering this state by running a scheduled task every 24 hours, when it sends me an email. At least this has worked for the last 2-3 weeks.
I have done a boot-time scan with the most recent versions of antivirus sw avast! (Alwil), G-Data (Germany), Housecall (Trend Micro), Stinger (McAfee) and Norton AV 2010 (Symantec). All scans were full. No viruses were detected. I have also done a full scan using Malwarebytes, nothing detected. I am uploading a HijackThis log run on the one computer located outside the school.
I am not sure this is virus-related, but I cannot think what else might be causing it. Thaks for any help or suggestions if I have mis-post.