I cannot get QB to show the current balance of an investment account. I enter the G/L as a journal entry. But my PL statement always shows an old balance. suggestions?

The balance of your investment account will show on your Balance Sheet, not on the P&L statement.  

If you are looking at your Balance Sheet and the amount is wrong, I would check the date of the transaction as compared to the date of your Balance Sheet.  If you did a transaction on December 15 and the Balance Sheet date is December 13, the transaction will not be reflected on the Balance Sheet.  So double check your dates.

Run your Balance Sheet report. You are asking about an Asset account. That isn't on the P&L.