Hey all,
I'm the friend Yodle spoke of. His description of the bug is a bit off, however. We have client crashes for everyone in the server whenever certain blocks are modified, but it doesn't happen only with torches. Placing or removing dirt, stone, and machines, etc has the same effect. Also, it doesn't have to be near solar panels (the second screen shot involves placing or removing blocks near pipes from BuildCraft).
I'm providing screen shots with some of the blocks that crash the game in the hopes that it'll help.