Hmmm, new firmware exists to solve problems, not create them. Something else is on play here but it sounds like you don't want to go that route. So let's take the easy one. It may still be on your system. Do this...
1. Open the Device Manager Control Panel
2. Browse to the device whose driver you want to roll back. Double-click the Sony BR player
3. On the properties screen, click the Driver tab, then click Roll Back Driver and follow the wizard to revert to the previously loaded driver.
4. A restart will be required.
If the option is grayed out, an older driver is not available. If you know that the driver has been updated, you may be able to recover it by using Windows' System Restore function, which will also undo driver installations.