Thanks for the extra info. First you should please try upgrading to MultiChain 1.0.8, in case that solves the problem. If not, try running MultiChain with these extra options:
-debug=mchn -debug=mcblock -debug=mcapi -debug=mcminer
Then after it crashes, send the debug.log file in the blockchain directory to multichain dot debug at gmail dot com and we can take a look.