Reaper almost always crashes when loading a project if a project is already open. Loading the same project after the crash always works. Here is an example of a crash event :
Alas the crashing module did not identify itself ("unknown") but that is very likely a plug-in anyway. Did you install 3rd-party VST plug-ins in \REAPER\Plugins or \REAPER\Plugins\FX by chance (you should not)? Other than that, maybe the culprit shows in an older/another event log?