You need to use better media, burned slower. Errors at the end of a disc like that are *classic* signs of bad media. Memorex is pretty much considered garbage (they just resell whatever they can get cheap from manufacturers).
Try to find some Made in Japan Fuji discs (look near the UPC code for country of origin) or some 16X Verbatim discs. Those are both pretty good discs (try to just buy a small pack at first) and will help test what's going on.
For testing burns, don't burn faster than 1/2 the rated speed and see what happens. (I.e., no faster than 8X on a 16X disc)
It's quite possible the reason you never had this problem before is you got lucky and got a spindle of "good" Memorex. The problem is it's impossible to know when they repackage decent discs and when they're repackaging garbage.