Common sense, due to the fact that the number loss was - apparently - done for legitimate reasons, and long prior practice would dictate that - certainly if you are keeping it - that there should be no problem whatsoever, especially if the number is below the antique cut-off, which is around 152000. There are laws about defaced and removed serial numbers, but I do not believe any reasonable person would apply them to your (quite common) plight. I'm not an attorney, but I'd think you should be OK.

However, having said that, with the pack of thugs we presently have for a government, I'd say that anything is theoretically possible, right down to the worst case of an ATF storm-trooper kicking down your door, confiscating the rifle, and jailing you. There is no telling what the present administration will try to do to firearms owners by executive decree. We must clean house in 2012. An Obama unfettered by reelection concerns (unless he abolished the two-term limit!) would be a total disaster for gun-owners.

Sorry for the rant - but see how a totally innocent act can possibly lead to trouble.