The problem is very unclear, 

I have a `server`, that constructs queries and post it to oracle to get response.
The oracle `database` is located at hight perfomance server:
`Linux 2.6.18-194.el5 #1 SMP Tue Mar 16 21:52:39 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux`

The `server` was tested on different locations inside of the intranet, including that high perfomance server, where the `database` is located. 

Several versions of the `server` (from old to newes) was tested also.

The problem: 

When the `server` posts query to the `database`, it have to wait for about 300 seconds to get response and construct logged output. 

But when I'm connecting to the `database` with pl/sql developer and posintg that query under this IDE, i'm getting a response less than one second.

Is there someting familiar for you, guys ? 
We're just cracked our heads trying to determine where the problem could be located...

If you need more information - I'll update this post immideately.