I've been using Harbor Freight blades for several months now.. I have had no problem with them. Could you possibly have both blades in the cutter? There are supposed to be two in a package, did you get both in there together? I did that once and my cutter was cutting awful!!
It could also be that you just got a package that was not as good as usual.. I haven't had that problem either, but I suppose it could happen.
I say just try another blade, they are a great price!