Quicken 2006

I did my first qfx connect download from my community first credit union website. It automatically entered all my transactions from 1/1/06 to date as I asked it to on selecting date range. The balance ending on my December statement and the opening balance for the register in Quicken are about $300 off. I want to give it a few days to see if this is due to something I am not thinking about. My question is would I be ok to change the opening balance in the Quicken register manually? I get a warning about "you are recording a transfer back into the same account".