Borrow a different keyboard to decide if it is the keyboard or the computer at fault and let us know.

Yep. It's the keyboard. I tried an older one and it works fine. I turned the problem keyboard upside down and hit it a bunch (in case something had fallen in it) - but it still doesn't work.

It's a logitech wired wave keyboard - which I love - but is probably only around $50 to replace. I made no changes to my computer (no updates, etc) for several days and the problem just started this morning. Is there anything else I can do to unstick the keyboard - or should I just get another?

Thanks.
Lynn.

Disclaimer: this almost certainly will not work. I'm posting it mostly as a curiosity from an earlier time.

Back when keyboards cost more than a service call we would first blow it out with compressed air and then turn it upside down and shake it as someone has described and then, if indicated, initiate a service call.

When the cost of keyboards dropped below that of a service call and the keyboard was probably trash anyway we would put it upside down on the top shelf of a dishwasher and run a cold water rinse. Then let it dry in a warm place turning it several times. This worked occasionally as the problem was often spilled soft drink.

As you have nothing to lose you could wash it in warm soapy water, rinse well and be very sure it is dry before plugging in. You will not be the first to wash a keyboard, and remember it is not working now so you have absolutely nothing to lose but much to gain.

Logitech wave keyboards run from $44 to $62 Canadian, quite a bit less in US dollars.

I have seen many people put the keyboard (only) in the top of the dishwasher and put it on cool water rinse only, do not run it through a dry cycle the heat can warp the plastic. I have not tried this but as stated if you can not get it to work anyway not much to lose, but make sure it is real dry inside.

things it could be... a stuck function key, try hitting all of them strongly, your numlock is stuck try turning it off and on also try that with the scroll lock key, look for any changes in language in the keyboard settings area, check any special keys on that keyboard to see if something got hit by accident and turned on, make sure all the regional settings are set for US not UK,
Go to control panel->regional and language options -> Languages tab -> then add the Us layout and delete the Uk layout, make sure it is not set to US Dvorak. It will ask to restart. You might also try hitting the left side Alt and Shift together, some times there are some custom set keystroke combos that get weird.
you can also try this to see if it shows your keyboard layout properly
goto start
then click on run
the run window will open there you type osk
then press enter

try unplug the keyboard, then restart the computer and plug it back in

another keystroke combo that can cause mixups is
NumLk ScrLK + shift key together

this was one of the most common problems I found when searching.
open Control Panel, and then Regional and Language Settings. Select the Languages tab, then click Details. In this new dialog box, there should be a tree view with a language (probably English (United States), and Keyboard underneath that. Under Keyboard, there should be US (in bold). Anything else under keyboard, you can remove (United States-Dvorak would be the one causing you problems).

well try all that and see if any of those might help, if not and the cleaning does not help I fear it may be time for a new keyboard, but you can certainly go to the website for that model and ask there for assistance.

Clean your keyboard in the dishwasher