MOVIE MAKER SLOW/HANGS UP WHEN SPLITTING AND TRIMMING

I started using Movie Maker a month ago and had no problems splitting and trimming clips, but now it is hanging up/going very slow and sluggish when I bounce around from one part of the movie to another.    When I try to split the movie it takes very long, several seconds to respond.   This makes it impossibly long for me to work on a movie that requires several splits.    I already had someone look at my computer for viruses and that was not the issue.  Also uninstalled and reinstalled Movie Maker twice and that is not the issue either.   PLEASE HELP THANK YOU!