You've probably got a burr on your spindle that's cutting the edge of the seal. You could remove the hub again, polish the spindle with emery cloth, then put back on and try again. Could also be a worn out bearing, either side causing it.
EDIT: Also mic the spindle and make sure the seal is the right size. I learned long ago that you can get in trouble using the number from the part you removed. It may not have been the correct seal to start with.
If you'll mic your spindle where the seal runs, I'll give you the correct seal part number. It will be tomorrow on that though.