Are you running this app from a shared folder on network.
If not, the location from where you are running it, try checking
the permissions granted to your app using caspol utility's rsg and rsp
switches. If your file writing code is in a seperate assembly that
your application loads, check the permissions granted to that assembly
seperately. Do write back if you r still feeling lost, this certainly
is not a case of .NET having any grudges against you.