Function key on my acer laptop is always pressed

While typing normal keys I have to press fn (function key) as it seems that the function key is pressed all the time.

What do I have to do to turn the function key off and it trigger it only when I press on it.

Finally I got the solution, after doing some random key pressing!

Infact there was key numLk, so i again press Fn+numLk and my keys started working properly.

Try to press ESC(FnLk)+Fn. This help for my Ubuntu 14.04 LTS + Lenovo Thinkpad E540.

There might be a setting in your BIOS for this. I know that some laptops use the F1-F12 keys for special functions and require the function key to be pressed for normal key use. Try running your BIOS setup while booting and look for an option you can change.

Lately I've been having the same problem across Ubuntu 10.04 (LinuxCNC edition), 11.04, and the late stable 12.04. I have an Acer Aspire 4535. The combo Fn + numLk doesn't work and my BIOS doesn't have any key customization, and then I've found the error message about Compiz in Ubuntu 12.04 and tried reinstall it with the following command:

sudo apt-get install compizconfig-settings-manager

And now the Fn key is back under control. I almost thought this was a hardware problem. I'm a newbie using Ubuntu so i don't know what actually happened to Compiz, it just works now.