Hello Marc

Please give more details on what kind of form you have, where you publish,
any dataconnections? Did you make any changes ecently, How you are accessing
the form? etc

Hi Marc,
 I certainly know the feeling!  One thing I've done is to add changes to a
working form in very small increments.  That way, when something quits
working, I know exactly which change broke the form.

 If you're getting the error from the browser version, force it to open in
the IP client; sometimes you get a little more information there.

 I've also started using the "stop processing" checkbox on an action for a
rule when I suspect the problem might be there.  I usually start at the last
action of the last rule on the submit and work my way up until the form
doesn't generate that error.

 I wish there was a better way to get a detailed error message though; one
of the only problems I have with infopath!

Good Luck!
Brian