I have Been playing the Modsauce pack on the ATlauncher Latest version of pack which uses. (1.0.0.5)
Blood Magic-v1.2.0(1.7.10).jar and BiomesOPlenty-1.7.10-2.1.0.993-universal.jar

I'm not sure if there is a proper naming system, but the Blood magic spell which you can turn blocks into falling sand entities appears to often crashes both Single player & Multiplayer servers when used on BOP Blocks. I have been able to reproduce this bug on several occasions with a few differn't BOP blocks.
Due to its nature of this bug it leaves the world unplayable because I would describe the falling entity block as corrupt, and it will keep crash the world as soon as its loaded.

Here is 1 of the crash logs that forge generated. I hope this was the correct place to submit the bug, I'm not sure the hermitcraft craft guys have any proper place to submit problems like this.
http://pastebin.com/XGuUfcmF