Alt + tab and volume error.

Hi everyone,
About 2 days ago i started getting a problem using alt + tab to change windows on w7, it flickers off after about 1 sec and also lowers the volume about 5-10% for pressing alt.
I have not installed anything for several weeks and i have no clue why it does it. Also the sound windows makes when i login and other sounds had changed without me changing them (im the only user on this pc).

Windows 7 Profesional 32bit.
NVIDIA GeForce 210
NGS Trail-Blazing keyboard

If anyone has had this problem before or knows what it is please let me know.
Thanks.

I just started experiencing this issue myself. Then I remembered, it's actually not a bug. Right click on Volume Mixer, select Playback Devices, select Communications, once you are there set the default to Do Nothing. Apparently windows has a feature that reduces the volume of any audio playback program once you start using any voice communications. I just started playing an online game using voice communications and it started doing it again.