The problem is likely that you are running a very old unsupported version of ADS on a much newer PC. This happens most when using something like Windows 7 on a recent PC with a multi-core processor. At the time ADS 2009 was built for Pentium 4 processors which only had typically one or two cores. This code would not always be optimum for the newer configuration. Try limiting the simulation to fewer cores. This will slowdown some ADS operations but it should run. The alternative would be to use any later version of ADS which all support Windows 7.
With ADS 2009 running and a Momentum simulation attempted but still open start the Task Manager (right click on taskbar and select Task Manager...). Find the hpeesofemx.exe process, right-click on that process, select Set Affinity... and select only CPU 0 or CPU 0 & CPU 1. Make sure any other CPUs are unchecked and OK out and close the Task Manager. Now restart ADS and the simulation should be successful.