Pass-trhough authentification checked - The network connection to your application was interrupted

Hello,
I already post that in citrix forums, but I want to try here also.

I have a simply but annoying problem
I have a MPS 4.0 and Using PNagent 9x i have NO WI installed, just I am using the PNagent 9x on workstations/laptops.

While users are connecting to applications using the PNagent plugin, the "pass-through authentication" is checked and they are receiving an error message "XXXerror : The network connection to your application was interrupted. Try to access your application later, or contact technical support.”

If users unchecked the pass-through case on Pnagent. it prompts to username / passwords / domain and they can work. so for the moment I told all users to do it in that way until solve the problem.

I checked different posts and I already tried a lot of solutions but whit no result. so for the moment I do not know WHY this error message while checking the pass-through case.....

Somebody Knows what can I do in order to solve this issue ?

thanks !