Hotkeys somethimes not working in Blender 2.75a

I am new to Blender, so this may well be something I am the cause of, but quite regulqrly the shorcuts don’t work anymore. Simple things like Tab, Ctrl-Tab, E,…
When I choose the function or tool from the interface, everything works as it is supposed to.

This may be linked to some other software that uses the Windows registry and gets priority. But before I try to find out more, I would like to know whether there are other people experiencing this and eventually whether it is indeed locked to other software.

It is not a great annoyance – coming from Modo I am used to other things - but still.

I use Windows 7 Pro 64, and the softwares that are open together with Blender are XYPlorer (a replacement of Windows Explorer) VLC player (to follow tutorials) and Firefox. I use of course Blender’s latest build.

Apart from that, I have not (yet) met with any crashes or so, and I must say I really love the idea of using all three mouse buttons.

Blender is extremely picky about the position of the mouse cursor while hitting hotkeys…
If you want e. g. to trigger an extrude command by hitting E, make sure your mouse cursor is hovering over the 3D viewport while pressing the key etc.

Thank you for your answer. This is something no tutorial seems to mention, except when it comes to maximising viewports.
I’ll pay special attention to it.
Each software has its peculiarities, and it is question to learn to know these.

Thanks again!