You are most likely running int this issue.
http://www.larian.com/forums/ubbthreads.php?ubb=showflat&Number=508558&page=10This could be the case with you having a 32bit system and/or a low amount (less than 4GB) RAM.
If the 32bit case is at fault, simply do this:
http://windows7themes.net/en-us/32-...increase-ram-used-by-single-application/It will free ressources reserved by the system.