Permissions problem

I have developed a webapp using JSP and POJOs that accesses our production Postgre database.  On the Windows machine I developed it on, everything works fine: it connects to the database and performs the queries specified by the user in the web pages.

When placed into production on our Linux boxes, it will not connect and I cannot figure out what the problem is.  I presume it is with permissions.  Other JSP webapps on our server successfully connect to Postgre, but using a legacy API I cannot get my head around.

Again my question is: Why does this webapp work when ran from my Windows machine, but not from the Linux?

thanks,
Jonathan