Quick Fix For “There has been an error while loading the form”

I’m testing a custom SharePoint Designer 2010 activity this fine Sunday afternoon and I was unexpectedly hitting a “Critical Error” when trying to launch the workflow:

There has been an error while loading the form.
Click Start Over to load a new copy of the form.  If this error persists, contact the support team for the Web Site.
Click Close to exit this message.
Show error details

Of course, if you click the “Show error details” button all it does is show you a correlation ID:

* In my case, this turned out to be an Alternate Access Mappings problem.

* I looked at the log file in the 14 hive and saw that InfoPath was complaining about an AAM issue (since I was hitting Localhost instead of the server name).  I changed my URL and that solved it.
Ex :

* Here the problem in this case was with the URL. First I was giving the below URL:
http://win-pfcp2dgt8di/_layouts/15/FormServer.aspx?XsnLocation=http://win-pfcp2dgt8di/MyTestFormLib/Forms/template.xsn&SaveLocation=http%3A%2F%2Fwin-pfcp2dgt8di%2FMyTestFormLib&ClientInstalled=false&DefaultItemOpen=1

Then I gave the below URL and it is working now.

http://win-pfcp2dgt8di/_layouts/15/FormServer.aspx?XsnLocation=http://win-pfcp2dgt8di/MyTestFormLib/Forms/template.xsn&OpenIn=browser&SaveLocation=http://win-pfcp2dgt8di/MyTestFormLib
It does to show that with all the linkings of the various bits now in SP 2010, the thing you naturally this is a problem (SharePoint Designer workflow in my case) is actually totally unrelated to the core problem.