Currently using this version below :
Multisites for Joomla! 1.5.x
Version 1.2.46 (Latest available: 1.2.46)
Patches definition Version 1.2.52 (Latest available: 1.2.52)

I have a problem on this notification "Unable to create the alias. Perhaps it is already". Every time I created a new clone site this notification will always appear. I tried to enter an alias not similar to any other alias. Same scenario, this notification will just appear. I frustrate me.. I need your help.Your response greatly appreciated.

Thanks,
Norman

This mean that you specified a "full directory" where create an alias (Symbolic Link) that point to the "deploy directory".

So if you are trying create website from the front-end, you could for example use
{root}/{site_alias}

I had changed "deploy directory" to {root}/{site_alias} but i still having that same notification "Unable to create the alias. Perhaps it is already". No idea what's going on.

This is my Website Template Details.

ID: basic
Group: front-end
Title: Basic Site
Description: Food Tabs Basic Template
List of domain names (*): www.foodtabs.com/{site_alias}
http://{site_alias}.foodtabs.com

Template site (*): basic(foodtabs_basic,jos_)
To site ID (*): {site_prefix}
Admin User (*): ftmyadmin
New DB server: localhost
New DB Name: foodtabs_{site_prefix}
New DB User: foodtabs_{site_prefix}
New DB Password: ****************
New DB Prefix (*): jos_

Deployment folder: {root}/{site_alias}
Create the deployed folder: checked
Alias link: {sit_url}/{site_alias}

This setup is for Creating a website from the front-end.
Any idea about this Sir?

This is NOT the "deploy directory" that must have the {root}/{site_alias} but the alias field.
Deploy directory = {site_dir}
Alias link = {root}/{site_alias}
This is a symbolic link and not a HTTP that must be provided in the Alias Link.
This is the location on the disk where you want create the Symbolic Link corresponding to the http URL.

So if you HTTP URL that you want to get is
{sit_url}/{site_alias}
The Site URL correspond on the disk to the location {root}.
So the link is {root}/{site_alias}

it works now.. but i have encounter a new error. "SITE_DEPLOY_CREATEUSER_ERR". Any idea?

When i tried to create a clone.. It had created a database but not user. Not all the clone files had not duplicated. Also having this error "SITE_DEPLOY_CREATEUSER_ERR".