My side covers both broke when I first brought my new V11 home. 3 years later my warranty replacements haven't shown up. Looks like I'll be repairing mine.
I have had great results with solvent bonding for small cracks. Not great for holding together things that have broken apart, but perfect for cracks.
Using a toothpick, dab a TINY amount of MEK (methyl ethyl keytone) along the back of the crack. Let capillary action draw the solvent into the crack. If you are careful, the crack won't even be noticeable through the painted side. Keep it off the paint.
Get used to it in a corner of the back, or on some scrap abs. Place a drop on the abs and scratch the toothpick around in it. You'll see that it melts the ABS and then it hardens back up again. You are essentially welding it back together.
Once it has hardened (best left 24hrs) use Steve's preventative measures as above along with rubber or nylon washers on the mounting screws and you should never have the problem again.
I have MEK in my lab (100%) but I believe that you can also get it at an auto body shop, or in the plumbing section of any hardware store. Look on the chemical contents of any "abs pipe solvent". I think most of that stuff is 99% MEK.
cheers,
Rj