|Well, I've never tried this on a SOHO router before so I can't confirm whether it will, or will not work, but the only way you'd be able to do so is if you can find the previous version of firmware that you were using.|
In your situation, I'd probably check the manufacturer's downloads and if it only showed the most recent version available (as I suspect it will) you could try contacting their support people to ask about the chances of getting an older version from them.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.