Unable to design my own form - "Infopath has encountered an Error.

[gummih]

I've been developing a rather simple Infopath form. It's just a form where
you put in a security number and a web service looks up the corresponding
address. This was all working fine.
Now something has happened so when run the form from visual studio I get the
descriptive error message "Infopath has encountered an Error. The operation
failed" and the form doesn't load. I can however open the .xfs file and fill
out the form, the web service works just fine there but when I press the
"Design this form" button I again get the error "Infopath has encountered an
Error. The operation failed".

Any ideas of what could be causing this?

br.