Try the easiest first: Get some compressed air and try blowing any dust out of the BR player's ethernet jack. If that doesn't work...
Take your BR player upstairs and try connecting it to the old router with a couple different ethernet cables. If it works, then you know the problem is the cable you have going upstairs through the floor. If the cable is marginal, it can work fine with one device but not with another.
I've frequently seen this problem (works with one device but not others) with cables which are mis-wired when crimping the jacks, so the signal pairs are are no longer transmitted on twisted pairs. Notice that the green pair is actually 3-6, not 3-4 in the following diagram.
http://1.bp.blogspot.com/_Ndsxv_4TBK0/THIJbkoq6bI/AAAAAAAAANw/IE0dApaTmuo/s1600/568B+configuration.jpg
If it's still slow, you know the problem is the old router or the BR player. Try plugging the BR player to the main router. If it works, you know the problem is the old router.
If it's still slow, then the problem is likely the BR player. You'll probably need to get it exchanged or fixed under warranty.