Not sure exactly what the large task is you're trying to do, but here's some workarounds I go to when Mike Urban crashes while trying to do something with a large number of elements:
[list]
[li]If it's something just involving the tables, try using Microsoft Access, possibly using an Action Query of some type[/li]
[li]If it's something geospatial, use ArcGIS Desktop, it's a little more robust with large numbers of elements[/li]
[li]Compact and repair your database in Microsoft Access before attempting the task[/li]
[li]Close and re-open Mike Urban so the Mike Urban instance is fresh (at least in my experience, the Mike Urban process usually hangs when you exit, so go into Windows task manager, and kill it to truly restart from scratch)[/li]
[li]You may also be able to use the Import/Export tool's Advanced functionality to write some scripting to do what you want for certain tasks[/li]
[li]If you're ok with SQL, you may be able to use the Tools > General SQL Command... tool to directly edit the database (usually, Microsoft Access works a little easier if you're not too familiar with SQL)[/li]
[/list]