Keyboard loses focus

My keyboard, from time to time, loses focus for no reason I can find. I can type, but nothing appears on my screen for a period of time ranging from a few seconds to half a minute, then suddenly it all comes, including the extra things I've typed, trying to sort out the problem.

I've checked the error records, and found nothing there. I've turned on task manager, and set it to stay on top, with the result sorted by CPU usage, but it rarely shows more than a few percent of CPU in use, and nothing pops to the top in any consistent way to show what is holding up my keyboard.

Is there some program or process I can invoke to find out what is claiming focus from my keyboard?

Thank
Don

Tech Support Guy System Info Utility version 1.0.0.1
OS Version: Microsoft Windows 7 Home Premium , Service Pack 1, 64 bit
Processor: Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz, Intel64 Family 6 Model 58 Stepping 9
Processor Count: 4
RAM: 3792 Mb
Graphics Card: Intel(R) HD Graphics 4000, 1704 Mb
Hard Drives: C: Total - 121432 MB, Free - 65283 MB; D: Total - 25000 MB, Free - 19716 MB; E: Total - 75000 MB, Free - 66600 MB; F: Total - 149998 MB, Free - 63951 MB; G: Total - 89999 MB, Free - 69542 MB; Q: Total - 13999 MB, Free - 2352 MB;
Motherboard: LENOVO, 2359CTO, Not Defined, 1ZSF434E1MJ
Antivirus: Bitdefender Antivirus, Updated and Enabled