Space bar is not working, all other keys are working fine.

If space bar doesn work. then the space bar is failed keyboard. If letter keys move and work, space bar is failed.

Check to see if there is any debris underneath the keys. Use canned air or an air nozzle hooked up to an air compressor. Sometimes, debris can get underneath the keys, keeping them from depressing the membranes underneath. If that doesn't help, you may need to take it to a technician to diagnose the problem.

That seems strange- try restarting your computer, or if that doesn't work, check your browser settings and make sure you don't have a weird key-bind set to the space bar. If all else fails, it might be easier to just reinstall your browser. I recommend Firefox, but Chrome is a strong browser as well.

wet replace keyboard

REPLACE THE KEY BOARD, THE PROBLEM WILL BE SOLVED.
REGARDS.
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it could be a virus , please scan it with a good antivirus program

You can easily fix your space bar. I fixed mine last month when my daughter pulled it out of the keyboard. I used this video tutorial guide to help install the space bar key back into place. Its really very simple. have a look:
http://www.laptopkey.com/installation_guides.php

on the upper L.H. side of the key board ther is a button marked MAR REL. turn typ. on press the return key then press the MAR REL key back space to move the carrier backwards or space bar to go forwords. when you are at the spot you need to be fined the button that reads L MRG. press it know your left hand margin is set,

know space the carrier over to the left by the space bar if it stops befor you whant it to press the MAR REL button space to where you whant.

now you have another button saying L MAR
press that and you left hand margin is set. Or the R MAR has small green letters saying L MAR if so you need to hold down the CODE key wile pressing the R MAG key ( any thing in green on key board can only be actavated by the code key ) hope this works

The space bar key is connected tothe keyboard a little bit differently then any other key.

There is a metal retainer connectedto the space bar key (on some keyboard models). Separate the retainer from thespace bar key with a flathead screwdriver.

Install the retainer back inplace as it shown on the picture. You have to engage the retainer with thesmall hooks on the keyboard.

Put the space bar key back inplace and gently press on it with fingers until it snaps back in place.

That’s it. The space bar key isinstalled back in place and should work as before. If you still cannot fix yourkeyboard, then you’ll have to find a new oneand replace it.
Pleas rate my solution on fixya if you are done.

Which kind of razr is it? If its a Verizon/Alltell the space bar is the # key.
If that doesn't fix it you may have a bad keypad. Does the # key work all the time?
If i can help let me know!