Strange Issue - Joomla multi site

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PHP

CMS

domain

We are using Joomla 1.5.20

Joomla Multisite Verion 1.2.8 - Free Version

Our URl Master Site URL is http://usentrepreneurtoday.com/

for which we have different slave sites like

http://newyork.usentrepreneurtoday.com/

We are facing a strange issue.

The issue is that when we open our master site, the site is opening properly, but the different links in the master site takes to slave site links ( This is also not happening always mostly the links are pointed to master site and rarely it points to slave site and also the links is not pointed to the same slave site, this varies periodically, but at a time all the links are pointed to one wrong slave site