Hi Ingrid,
a quick google search on usenet revealed people with similar issues.
for example
http://groups.google.com/group/microsoft.public.infopath/browse_thread/thread/28e4488aaa0d442d/f62d354bf73135e7?lnk=st&q=%22does+not+resolve+to+a+key+for+the+Identity+Constraint%22&rnum=1#f62d354bf73135e7
quote:
1. I used winrar to open up the .xsn file and put all the individual files
into a folder
2. i used textpad v4.0 to open up the manifest.xsf file
3. i looked for "ruleset_7" and found what appeared to be a button control
that had no rules or expressions for it. I guess for some reason InfoPath
just didn't like this and kept generating the error. must have been a
leftover control that I originally placed into the form and then didn't end
up using the object, but for some reason the datasource stayed in the form??
4. I removed the entire set of code for the "ruleset_7"
5. i opened up the manifest.xsf in InfoPath and I was able to open the form
again, and resave it to re-package it back into an .xsn
where the issue was solved by editing the manifest:
whole search here:
http://groups.google.com/groups/search?q=%22does+not+resolve+to+a+key+for+the+Identity+Constraint%22
hth