Having problem in publishing InfoPath form

Question

Hi alll, I was having problem in piblishing InfoPath form to the SharePoint site. when I tryed to publish InfoPath form through InfoPath Publishing Wizard I got following error.
The following URL is not valid: http://servername:portnumber/sites/sitename
I searched over the internet abd dint not find any satisfying answer but figured out that most of the people are talking about creating site at root level means: http://servername:portnumber/
I creted site at this level and then try again, this time InfoPath Publishing Wizard validate the site successfull. I resume my task and get it done.
But I am still unable to understand why I need to create site at root level when I dont want to create it because of my desing?
Does any body have Idea why this happens? Any help in this reguards will bw heighly appreciated.
 
Regards
Ali Raza