EFopen error: Insufficient System Resources

Hello
I am using Windows XP 2002 Home Edition, Service Pack 3, 32-bit.
When I run the computer about for 8-10 hours, it would start showing the following error message:
EFopen error, insufficient system resources, exception unknown software exception, or out of memory errors.
The system is running fine but the Start Menu would go clear and all the Programs won't work at all as well as the Task Manager. It needs restarting and everything is fine for a few hours. But then it gets even worse again. I have also installed Avira Antivirus & Spybot on my PC. I ran Combofix, MGTools, CCleaner and some online scans in my computer but they failed to detect any error or virus. Still I am facing this problem and it occurs regularly. I don’t know much about this problem. Is this a virus problem or hardware? How can I fix it? Please help. Thanks in advance.
