The sequence was:
Install 2011 over 2008. Convert may quicken DB. Do several one step updates to a Capital One credit card account. Install R3 update to 2011. More updates. Reconcile.
Reconcile showed a cleared balance discrepency, which I eventually tracked down to the starting balance of the account being positive rather than zero.
I subsequently reconverted the 2008 DB and did an update. The starting balance is correct.
I do not know when the error occurred. I'm really not asking for help, just reporting this in case others see it, or know about it.
Nothing in the release notes indicates this sort of bug.