MS Natural Ergo Keyboard 4000 Sticky/Stiff Spacebar Fix

I recently replaced my old MS Natural Elite Keyboard with the brand new Natural Ergo Keyboard 4000. I was happy to get this keyboard but after setup I found that the pace bar was stiff and sticky. I tried to search web if there is any solution and I found one website saying to put lubricated plastic posts on underside of key. They also mentioned to twist metal sway bar away from each other slightly or to remove it completely. I tried this all but none of them worked for me so far.

Can you guys please suggest me something to fix it out? Many thanks.

I had the same problem with the space bar, but I finally solved it once and for all.

In the picture "Keyboard Under Space Bar" in your link you will notice that there are two tiny triangle shaped plastic protuberances in the black area below the zxcvb and nm keys (marked with an asterisk in the lousy ASCII diagram below, ignore the dots).

Z X C V B ··············· N ···· M
---------- ············· -----------
| O · O · / ·············· \ ·· O········
______ / * ············ * \________

In my keyboard one of them (the right one) was broken. I couldn't add the missing one, so I tried (please notice that this is what I did, I am not responsible of the results if you try this and something goes wrong. Try this at your own risk.) removing the other one with a nail clipper. I also strategically placed a folded Post-it note under the left part of the space bar to solve the other problem I had with the space bar: it was too noisy. Now it works just fine.

I have tried the above solution and I can verify it significantly improves the stiff spacebar problem. I actually had same situation with the right 'protuberance' already broken as well...

I also had the problem of the aggravatingly loud, squeaky/scraping space bar. I was quite surprised that when I pulled off my spacebar and started poking around, I realized that the little triangle protuberance on the right side was broken on my keyboard also, and was hanging down. How bizarre!! I took your tactic of pulling it off then removing the left one with nail clippers, and it completely solved the problem. It seems like a weird defect to keep repeating. Anyway, now the spacebar is fine and yes, this keyboard rocks!

I tried Audi's method and it works great.
When replacing the space bar, the swing bar (looks like it's made from a big paper clip) goes toward your stomach, rides on top of two rails, and slips under two tabs.

I added the 2 pads and its much better. I used a very thin mouse pad for material. But that only solves the problem of when the key is going down. Then there is the problem of the key return clacking noise. I wrapped electrical tape around the "sway bar" thing that may have helped dampen the resonance a bit but not much of a solution. The sway bar doesn't make so much noise I don't think. Removing the sway bar helps immensely but then the spacebar cannot be used on the sides. You have to make sure your thumb is hitting it more in the center. Doesn't work for me nor would I think it would for 99% of the population. Then I tried lining the bottom of the spacebar with electrical tape to minimize the resonance of the plastic. This helped quite a bit. Just make sure the tape doesn't interfere with the vertical movement of the spacebar! Later maybe I'll try other tape besides electrical. Or thicker tape perhaps. But this is a huge improvement. Its truly amazing that a company as advanced as Microsoft can have a product out for several years and not see fit to implement these very minor changes. A quiet keyboard is something most anyone would value. Now I'm noticing other larger keys (Backspace, Shift, Tab, Caps Lock) are noisy though for some odd reason the Enter button that would get used a lot isn't. Guess we need to look at the differences of each.
I should mention this keyboard is no joy to clean but I found that I didn't need to have the screws on the back for it to work fine. So that's better. You do need to have the 2 chrome screws attached under the spacebar I believe but 2 is a lot better than about 10 to get at the thing.
I'm attaching some photos of trackballs used with the 4000 keyboard. If you don't use the numeric keypad (and most of us never do) it makes sense to remove the keys and plop a trackball on top or a mouse on a platform of some sort. Think of how many times your right hand darts from keyboard to mouse a day. You do want to minimize that distance. This is where left handed people have a huge advantage.

Second solution ( "twist metal sway bar away from each other slightly") worked for me just perfectly. But not at once - I did it 3 times.
I also tried removing the metal bar completly but didn't like the result.
Thank you, Paul Michaels, for information.