unavailable Server RPC

[Gabriele]

Hi to all,
I am developing a c# application which should manage my mpp files and
microsoft project in general. in particular I'd like to :
open microsoft project
close microsoft project
open a certain mpp file
close the mpp file
and I should make any of these operation in a random order.
at the moment I use the following methods to perform these activities,
but when I call the fileopen method per the second time I get an
"unavailable Server RPC" message. where do I make the mistake? I think
( because of it happens only after the first time) that I don't clean
something...but what?
Any suggestion will be very valued!
Gabriele