Mouse Ceases To Work Properly When Clicking Buttons In Applications?

having migrated from XP to W7 (never experienced Vista). Quite frequently I encounter a problem with the mouse, in which it fails to (a) bring the auto-hidden taskbar into view, and (b) properly select functions normally controlled by button clicks. Problem arises once or twice a day on average.As background info, the computer is in use pretty well all day everyday, mainly for work. I work freelance at home as an electronic designer. Being technical, I understand computers to a fair degree, from both hardware and software PoV, though I don't design things that work directly in conjunction with computers. I'm mainly concerned with embedded systems, both hardware and low-level software, and I don't write programs for running on computers (programming skill is confined to assembly language and embedded C).As a typical example, I suddenly find I can't bring the taskbar into view by moving the mouse cursor to the bottom of the screen, in order to switch from a Word document I've been working on to find another document in Windows Explorer. So I use Alt-tab to switch to Explorer. But if I now open a new document (eg a pdf), I then have to use Alt-tab to return to the Word document.However usually that isn't all that goes wrong, as I now find that clicking on something in the word document toolbar (eg to go from 'Home' tab in MS Word to the 'Insert' tab) doesn't work. All that happens is that Word goes out of keyboard 'focus' - the blue background to the toolbar goes grey, and I can't type anything. I then have to use Alt-tab to re-select MS Word (cycling through all the open windows) to bring MS Word back into focus. Since I can't use the mouse for selecting, I have to press Alt, then tab or arrow key to step through all the toolbar buttons and options till the one I want is selected, then press Enter on the keyboard. In other words, I'm reduced to keyboard-only mode.

Sometimes I can get out of this situation by closing one or more windows I don't currently need (by Alt-tabbing to bring up a window, then pressing Alt-F4 to close it). In extreme cases this won't cure the problem, and it remains in keyboard-only mode even with only one application open. The only thing I can do then is to close everything, switch off and reboot - even Restart is not enough, I actually have to switch off and on again.Has anyone else observed this behaviour with W7 or is it just my computer? I don't think it's a problem with the mouse itself: the cursor always moves around the screen normally, and I do get a response by clicking on a button. It's just that the response is wrong, it simply takes the whole application window out of focus so clicking no longer does anything in that window.