Here is what I did:
1. Used new portfolio wizard to create new portfolio
2. Retrieved all past transactions
3. Manually went into 2 investments and added a "split" in the data register
4. Edit - Internet Retrieve - Transactions - etc.
What I see are the original transactions associated with step 2 above for the investments in step 3. Even if I import them, the next transaction retrieve grabs them. The main annoyance is I have to manually un-check these transactions every time I retrieve transactions for the entire portfolio.
The split I added comes after all the pas transactions (brk.b 50:1 on 1/23/10 and aib 82:412 on 2/22/11).
I don't know why the system does not ignore these past transactions, since, they are already in the data register. The retrieve function will just let me add the transactions over and over again, incrementing the number of shares upward.