Why does InfoPath take 30+ seconds to open?

If you are using InfoPath in SharePoint, then you'll definitely want to read this if your InfoPath form is taking more than a few seconds to open or publish.  This applies to both InfoPath 2007 and 2010.

As long as the InfoPath form doesn't have a bigillion rules/views/fields, then you should be able to publish the form to MOSS/SP 2010 (as a form designer) in less than 15 seconds.  Users should be able to open the form in just a few seconds - typically less than 5 seconds.

Solution: In Internet Explorer (IE) settings, uncheck "Automatically detect settings" in the Local Area Network (LAN) Settings. 

Here are a few screenshots on how/where this is located:

1) From the IE tools menu, select "Internet Options"

 

2) Click on the "Connections" tab.

3) Click on the "LAN settings" button (highlighted above)

 

4) Make sure "Automatically detect settings" is not selected.  

Once "Automatically detect settings" is deselected, your InfoPath forms should open very quickly, and saving them back to SharePoint should be pretty instantaneous as well. 

According to Microsoft, "If the Automatically detect settings check box is selected in Internet Explorer, the Windows Update client uses the WPAD feature to locate a proxy server."  If you happen to work for a company that requires this setting to not be changed, then please post a comment.  I would also like to hear if anyone does NOT have any InfoPath loading issues if this IE setting is selected.

Also - I don't have enough evidence at this point, but making this LAN settings change may also resolve an authentication issue where users are prompted to log in once to open the InfoPath form, and again to save it.