Courtesy of the makers of DIF: http://www.zinsser.com/ProjectDetails.asp?ProjectID=23
Just so you are on the same page, read the link I just posted. I know the key to removing wallpaper of ANY type under ANY conditions (including painted wallpaper), is to be sure you're allowing the mixture to get UNDER the wallpaper. It sounds like you're having this problem. You didn't mention anything about using a Paper Tiger. (See the WEB site.) You need to perforate the paper. Also, expecially if the wallpaper is vinyl or metalic, the DIF solution will NOT penetrate the paper, directly. Perforating the paper (or vinyl or the like) is key. Just don't press the Tiger so hard that you 'nick' the wall too much. You only need to press hard enough to perforate/break the paper's surface. You'll need to 'practice' a litte and inspect your paper-tigering efforts.
Personally, I'd use LONG, thick gloves so I can apply BOILING HOT solution. I keep a kettle of water on a low flame on the stove. I lay plastic on the floor, then I lay newspaper on TOP of that so whatever mess I make, I can keep off of my good floor. I use one of those HUGE car washing sponges that you buy in an Automotive Supply Store, like ADAP or Pep Boys. You need to follow the directions TO THE TEE.
You should perf the paper, about a section that's about 10' wide. Soak it GOOD w/the mix and wait 15 minutes. Then soak it again and wait another 15 minutes. Then, soak it a 3rd time and IMMEDIATELY start peeling.
TIP: While the first section is soaking during your first 15 minute wait, go ahead and perf a 2nd 10' section. WHen the 1st 15 minutes is up, go ahead and reapply the mix to the 1st section AND move right to the 2nd section giving it its first coating. After the 2nd 15 minutes, soak the 2nd section for a 2nd time and then soak the 1st section and immediately begin peeling the 1st section. The TIP here is to keep 1 step ahead so you're not always twiddling your thumbs.