I have two servers Windows 2000 with Citrix, when users use Application developped in Delphi, which connected to an Informix Base ( IDS 10 ) with AIX 5, it's OK !
But If they have inactivity during 30 minutes, they have message "Network broken". They cut Application and restart Application, it's OK !
On the same servers Citrix , i have others applications which use SQL-Server and I have NO PROBLEM.
I Think so than Citrix is not then problem because only 1 application has problem, and then 10 others are OK.
Only Application with Informix 10 has problem !!

Last week, All was OK, I have "just" changed Informix Server :

Last week : Server H50 with AIX 4 and Informix IDS 9.3
Now : Server P520 with AIX 5 and Informix 10.0 ( the new server is neraly 5 times faster than then H50 ).

Thanks for your help