time out inside server

Dear folks, 
 
We have been haunted by a very difficult problem which we cannot 
solve: 
I will try to describe it in few words as I have heard of it myself here.  
 
The server posgres is in windows and the clients access it though 
terminal service.  
When so many clients ( 8 at least) get connected, when one of them want 
to do some writing, sql, or consult in the database, there is an error, 
something like this, sorry they could not explain very well  -  code 5307 
cannot execute   ... is not valid in this contex  or  connection is closed - 
and after this error reexecuting the sql it works.  
 
What could be the reason for this error? 
 
We are using Visual Basic with an odbc driver for postgree. 
There is an interesting fact that we are accessing the odbc drive from 
inside a .dll called visualprotector, but I dont think it might be the most 
important fact in this environment, although I would not simply ignore it. 
 
It should also be said that it only happens when accessing through 
terminal service. If everybody would access it locally the error hardly 
happens. 
 
Also, another point that should be noted is that we also work in the same 
way with the microsoft sql server  and it doesnt cause any of these 
troubles. 
 
hope you are all well, 
thanks in advance for any help, since we are falling into despair 
because many clients are complaining. 
Please write as soon as possible, 
 
your truly, 
marcello miorelli