Certificate request problem - Error 0x00000046

I've already resolved this one couple of times, but never document it before...;)

Yesterday, one of my clients called explaining me that secure section (https) of the internal web site is "not working" anymore. They use combination of IE 6, IE 7 and Firefox browsers, and said that in IE 6 and Firefox browsers popup window asks from them to continue, and IE 7 displays the page where users are asked to click on Continue link.

Reason:
It was obviously certificate problem, and after further investigation I found that certificate has expired.

Solution:
So, I've opened IIS Manager on the local Microsoft Windows 2003 Server and removed current certificate from secure portion of the web site. After that, I requested new certificate with the same parameters from online certification authority (Certificate Services running on the same server), completed the wizard successfully...and...nothing happened ?. Certificate was not generated...!?

Restart of Certificate Services didn't solve the problem.

Then, I've tried the alternate method through %servername%/certsrv, Advanced Certificate Request -> Web Server. After completing the form, and clicking on Submit button the following error appeared:

Advanced Certificate Request:
 
"An error occurred while creating the certificate request. Please verify that your CSP supports any settings you have made and that your input is valid. 

Suggested cause:
You do not have write permission to save the file to the path Error: 0x00000046 - Permission Denied "

The problem was in permissions on local certificate store on CA server:
C:\Documents and Settings\All Users\Application Data\Microsoft\Crypto\RSA\MachineKeys

Administrators and SYSTEM group needs Full Control permissions.

Advice:
Renew your certificates before expiration.....;)