InfoPath Dev

Using InfoPath 2007.   I keep getting the error: Error 1 Type 'XmlChangingEventArgs' is not defined.  I've no idea how i got this error, not sure what I did. I don't use VSTA... I only know what its called because it pops up with this error! I am so frustrated! How can I fix this error? I am no ...

Thanks for the info, but I have deduced I am such a noob to infopath 2007 that I have no idea what I am doing. I did as you wrote, but still to no avail.    

I am extremely new to infopath and sharepoint. I have searched the forums trying to find a solution; my apologies if it exists.   My question is:  I have two lists, one of first names, the second of last names. I wish to have a drop-down list within infopath take the first initial of the the first name and combine it with the last ...