Keyboard Num Lock turns on/off during startup and shut down

Hello,

I don't know if this is an issue, but today I noticed my Num Lock turns on and off, not blinking but just on and off about 2 or 3 times when I am starting up the computer and when it is shutting down. Boots up fine and keyboard works, but I just found this odd.

The keyboard is just a generic Dell USB keyboard and I am running Windows 7 64 bits professional, my system is:

Saphire HD 7850 OC (at default OC)
i5 2500k (turbo enabled, i.e. 3.7 ghz while gaming)
16 GB Corsair Vegeance @ 1333 CML16GX3M4A1600C9B (but can activate XPM for 1600 but would this really help at all?)
Maximus IV Gene-z/Gen 3 Motherboard BIOS - 0402 (first released BIOS)
Blue Caviar WD 500 GB
Seasonic Semi Modular 620 W PSU

System works fine otherwise, although I had problems with the RAM before, but it seems to be ok now, just ran Memtest 86+ from usb for 6 hours with no errors. Prime 95 is also stable.

Other problem I found is twice when Windows Starts and I just reconnected my Keyboard (I disconnected it twice because was replacing RAM), the keyboard was responsive during bios but went unresponsive for about 5 seconds on the Windows Login screen, then it just started working, has not happened again though. The system was otherwise fully responsive during the 5 seconds the keyboard did not work, that is I was able to move the mouse click on the textfield etc.

Other notes: Keyboard always works other than those 2 times, and computer runs fine too. Also I am not sure if it just started doing this or if I just noticed.

Is this normal behavior or perhaps just bad keyboard?

Thank you,

Oscar