What are you using to make the form request (Workspace, servlet, etc)?
How big is the form (the file size)?
Which LiveCycle operation are you using to render the form (Forms, Output, Form Data Integration, etc)?
Are you merging data with the form? If so, how large is the data?
Is there anything unusual going on with the LiveCycle server? Anything in the logs, is the server CPU at 100%, etc.?