I would suggest the following for the moment.
1. If you only have 4GB of memory don't run any other programs at the same time.
2. You quit and restart every 30 minutes.
3. If you want to merge from Public Trees, type the details in instead. Allows a more critical approach immediately to the data.
4. If you are merging a gedcom, use the append only option and then manually merge the hopefully only one or two individuals who are duplicated.