WordPress MU

I installed the WPMU and I chose to use subdomains for new blogs.
When a new user signs up for a blog in the wp-signup page, he gets activation link email but when he clicks on this link, he gets page not found error: " Internet Explorer cannot display the webpage" page.
I read everything I could find on this forum about this kind of problem, and I insisted with my host provider that he verifies the configuration of the Apache <VirtualHost> and the wildcard subdomains in DNS according to the readme.txt. He says that the server is configured according to the instructions. But still, it doesn't work: the new blogs are not created!
Can somebody help me, please.
If you want to try, here is my website: http://www.simusonline.com/
Please help. Thanks.

Dupe post: http://mu.wordpress.org/forums/topic.php?id=6705

Well, when I look at a sub-blog, I get the "Great Success !
Apache is working on your cPanel® and WHM™ Server" message, so you've got a setting wrong on the server somewhere.

The fact is: when I check the files on the server via ftp, I notice that there are no folders representing the subdomains. For example: the validation email refers to: abc.simusonline.com/wp-activate.php?key=....... but the script has not created the 'abc' folder and thus has not copied the wp-activate.php and other stuff there.
The host provider says that it is a problem with wordpress while you say that it must be something wrong with the server.
Wordpress doesn't even give error message saying for example that it could not create the subdomain or copy the files in it.
I really do not know what to do!

"The fact is: when I check the files on the server via ftp, I notice that there are no folders representing the subdomains. For example: the validation email refers to: abc.simusonline.com/wp-activate.php?key=....... but the script has not created the 'abc' folder and thus has not copied the wp-activate.php and other stuff there."

That's because the "folders" are virtual, and don't physically exist.

MU uses mod_rewrite to serve the blog, whether you use subdomains or subdirectories.

"The host provider says that it is a problem with wordpress while you say that it must be something wrong with the server.
Wordpress doesn't even give error message saying for example that it could not create the subdomain or copy the files in it.
I really do not know what to do!"

It is a problem with your server. How can this be deducted when there isn't any information provided from the logs, or anything else to go by?

Andrea said: "Well, when I look at a sub-blog, I get the "Great Success !
Apache is working on your cPanel® and WHM™ Server" message, so you've got a setting wrong on the server somewhere."

So, that means 1 thing: The DNS works, as it points to the server, but when it gets to the server Apache doesn't know what to do with it. Which means that Apache doesn't recognize the subdomain, which it can therefore be concluded that the virtual host in the Apache configuration file (httpd.conf, for example) was not properly modified.

A rare case would be that it was modified, but Apache was not restarted after the modification.

Thank you, Guys.
Finally my hosting provider sorted it out. After so much headache!
Regards,
Simeon.