Some windows won't close from the taskbar sometimes

A minor annoyance, but for some reason there are windows that won't close

from the taskbar using the mouse right-click, then left-click on "close".

Alt-F4 always works, and so does using the red X in the top right, but when I

want to quickly close selected windows from the task bar, I often receive the

"blunk" beep (it is not followed by an error message of any kind).

There is not a detectable error going on, like a non-responding program.

This seems to happen randomly and then I manually close the window with the

"X".

I've experienced it with Internet Explorer windows as well as Windows

Desktop Search. It happens several times an hour so I thought I would see if

there is some setting error, or if I just need to close the old fashioned way

every time this happens.

Thanks