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I am running Windows 7 with Microsoft Security Essentials for virus protection.

Recently, the computer goes out to lunch for a couple seconds at a time, during which keyboard events and mouse clicks are gathered up and then after the processing resumes played back with a delay.

I checked the task manager and find that CPU is very low utilization, with system idle running between 30% and 70% of the dual CPUs that are each hyper-threaded.

Actual CPU usage is reported between 15% and 70%, there are 82 processes and memory usage is around half of the 3 GB of memory. The biggest consumer is Firefox taking around 1 GB followed by windows explorer with 341 MB and Adobe Bridge with 325 MB.

What might be going wrong? How can I figure this out and resolve it?

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up vote 1 down vote accepted

If the keyboard and mouse are not responding, then some driver is hogging up cpu time in kernel mode.

Look at my answer to Steps to troubleshooting a problem with high DPC, which details the ideas involved.

It's going to be some driver, the problem is which one.

i've heard of video card drivers on a laptop periodically checking if a monitor is attached, and blocking the entire system as does.

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Firefox taking about 1GB sounds like a big problem to me. If it is indeed taking up that much, your system may be hitting up swap space which could cause some of the lag that you are seeing. I would try shutting it down and then bringing it back up - particularly if you haven't done so in awhile.

Another thing to look at (which you didn't report) is what is using your CPU? Higher-than-average CPU usage by an application can give some indications as to problem areas.

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