While it is technically feasible to run multiple instances of TM1 under the same OS session, you do so at your own risk. This is because TM1 does not play well with other apps, even other instances of TM1, when it comes to memory. Each instance of TM1 is going to grab all the memory it needs (or thinks it needs in the case of using multiple processors in the cube loading and processing of feeders). If you have set the MaximumCubeLoadThreads to more than 1 TM1 is going to grab more memory than it actually needs. The more processors you set in this parameter, the more memory it grabs. You could be crashing due to lack of memory caused by the initial garbage memory being too high on startup of the instance. Either Use VMWare, or something like it, to separate the OS sessions, or drop the processors in the MaximumCubeLoadThreads, if you have it set to more than 1.