Here is information from the Knowledge Base concerning error 43.
Question: I have lots of RAM. Why do I sometimes get "Error 43, Insufficient memory"?. Answer: The problem you're having occurs on very fast machines (usually those with 200mhz processors). Error 43 appears when the Candidate Place or Candidate Individual window opens. This window opens when you click the Find button next to the spouse field of the Individual Record window, or when you type a name directly into a parent or connected individual field and that name is already in the project and then save the record. Later versions (2.7 +) have a redesigned Candidate Places window which will display only 250 records at a time. If the record you want is not in the list, type part of the name in the field at the top and click Find Again. You can use the asterisk wild card for this search. For example, if you want to find everyone with Kennedy as a surname, you could enter -- */kenn and then click Find Again.