I've owned a Canon XL-1 since 2002. Recently, the XL-1 (or Sony ME DVM60 mini DV tape) malfunctioned and recorded only the right 2/3's of the frame. The left side was completely black and a semi 'saw tooth edge". In addition, the camera recorded no sound. The 2/3's of the screen it did shoot was poor with sporadic artifacts rendering the footage virtually useless. I ran the head cleaning tape but it happened again. The numbers etched into the side of the suspect tapes have similar SN numbers...perhaps from the same batch? Not sure.
I'd avoid the head cleaning tape. Use only in an emergency. It's sand paper. If your heads need service take it in for a pro cleaning. Also if the heads are clogged try running a tape through in fast foward and then rewind. This often clears a clog without hurting the heads. If the tape is bad try a new batch and find out. If it's your cam, take it in for service.
OSX 10.3.8; Quicksilver Dual 1 gig; FCP 3.0.4; Sony camcorder vx2000; write professionally for a variety of media