I just managed to fix a DMD with 3 horizontal lines out. I had seen example posted elsewhere on the web of people drilling through the face of the glass to the point which the DMD pins connect with the board pins (which, in theory, are within a space separated from the actual "dot" space by epoxy lines that hold the glass together). It looked kind of risky and while I understood that the repair would generally not be visible, it did seem like the jumpers might interfere with the rubber baffle that keeps in light around the display.
I assume that my circumstance is pretty common. When I checked the pins coming from the glass, the one with the lines out were broken right at the place where they enter the glass "sandwich" (i.e., there are embedded in the thin epoxy layer). It is important to check to pin numbering so that you don't get confused. The Babcock DMD in my Pinball Magic has the order 32 to 1 top to bottom and 128 to 1 left to right when viewed in place. Thus, if top line is out, you might be confused that when you have the DMD out for inspection, pin 1 seems perfectly solid; you need to check pin 32 instead.
Anyway, I reasoned that there was less risk, drilling from the side along the path of the pin between the glass. I selected a Dremel diamond coated bit (7144) that was 3/32" max (the width of the pins apart) but tapered such that, given the distance in I planned to drill, the holes for pins next to each other would still be separated enough. I actually found that using a regular cordless drill to be about as effective as using the High Speed Dremel motor - certainly far easier to control when getting started.
Even though you are drilling from the side, it still important to protect the face of the glass from any slips. You will also want to gently bend the broken lead down the board and out of the way. Also I would start the hole just slightly above the epoxy line rather than right on it. The diamond coated bit chews through glass and epoxy fine but it not the best against the metal of the embedded pin. But in someways that is ok in that if the bit kind of goes in on top of the pin, you'll end up with more metal surface area to bond to. So when looking at the face of the DMD, you can clearly see how far the bit has gotten: there will be a white line coming from the edge through the dark of the epoxy. It is good to look from this view while drilling to make you are going along the path of the pin toward the connection within the glass. Though a little trial and error it seems like going about 3/4ths of the way through the epoxy line works pretty well - there's more space to fill with solder. In any case, you need to be patient as it does take a while to get to where you want to be.
Once the holes are done and blown clean, I secured the display on its edge I melted some silver solder paste (this is cheap as opposed to the epoxy) into the holes, and then also melted some regular solder into them. I did find that it seemed to improve the likelihood of getting the final bond solid to drill out the soldered holes again, perhaps by pushing solder into the roughened glass surface. But regardless, I first got solder into the holes and then I got some stiff wire of the type used for component leads (I cut mine off and old capacitor) and heated it with the iron while pressing on the solder in the hole until it slid in the length of the hole. It may take more than one attempt but with a little persistence, you'll get your new lead(s) in there nice and solid.
Once the solder is nice and solid, you should go test the connection. Touch a jumper from the bent down broken lead to the new lead and hopefully your line/column is back in business (if not, try again but I will say that every time I got a solid new lead in place it worked). If all is okay, you can bend the old lead back up into place and trim and bend the new lead down toward the board. The new lead length should take the end to the surface of the board so that you can solder the two of them together further from the glass to not risk softening that connection.
I think this process might get unwieldy if you had several lines/columns in a row to fix but I did manage with two right next to each other.
Finally I will say that I did a couple of other simple things that *might* help to prevent future breaks. As per Cliffy's suggestion, I added dabs of super glue to to point where the pins enters the glass for every pin (it didn't take all that long to do all 160). Second, I added thin but flexible spacers between the plastic posts that attach the DMD to the front panel which (only theorized) might dampen some of the higher frequency vibrations coming from speakers, etc.