Thanks for your report !
Firstly please check if Add-In Translator- DWF or Translator- DWFX is loaded or not in Add-In Manager 2011 dialog box, you can go to ribbon Tools > Options panel, click Add-Ins button to launch the dialog box.
Secondly please use Save Copy As command then you should see the DWF file type list, i attach two images for describe.
Thanks for quick reply.
I would like to inform you that, I used to create with the same procedure. But, I have got the new system (Windows 7 operating syetsem) with in which I can't see this option.
Please see attached screen shots of my Inventor 2011.
Thanks for your comments !
From you screenshot, seems add in Translator: DWF and Translator: DWFX are not loaded, can you try to set them to Startup/Loaded and relaunch your Inventor for double check ?
My inventor 2011 is installed in Win 7 OS and doesn't see your problem.
You can also use Export to DWF command to save to DWF file, see attached image. Do you have this command ?