Are you using FormsCentral in a web browser or from the Desktop application that is included with Adobe Acrobat Pro XI?
If you are using a web browser please try another browser or refresh the browser page and see what happens. In a web browser you should get a "Download" dialog with a save button that brings up a FIle Save As dialog allowing you to choose the name and location for the PDF...
If you are using the Desktop application with Acrobat, Acrobat creates the PDF so if you have a dialog open in Acrobat that would "block" any new actions so make sure you close any open dialogs in Acrobat and try it again. Acrobat will create a PDF and then prompt you to save the file.
Let me know which you are using and how it goes.
i am using the desktop application not sure what you mean by open dialogs nothing else is open
Before you save the PDF make sure that Acrobat is not running, if there is anything open in Acrobat close it. If you are "doing something" in Acrobat (say you have the "Open File" dialog open to open a file, or the Print dialog open from starting to print) then Acrobat can't perform the PDF creation.
When you click "Save as PDF Form" in FormsCentral you will see the quick progress bar you noted, and then Acrobat launches and creates the PDF and a "Save As" dialog will open up so you can give a name and location for the PDF to be saved.
Have you run Acrobat prior to trying to use FormsCentral? I am guessing that you have, but if you have not you should launch Acrobat and make sure it has been activated and can be used before trying to save the PDF from FormsCentral.