The most complete repository for DW and SC scenarios and campaigns to my knowledge is still subguru.com. It has a lot of missions, but not all intended for LWAMI. And it isn't allways shown for which mod or game version it was made. So there might be issues here and there. Most likely immediate detection at the start of the scenario. Just try starting the mission again and hope the Random Number God (as someone else here described it) favours you.
http://www.subguru.com