Why is PowerPoint so slow, and why does it keep creating "temp" files ?

This is a recent problem which does not seem to be manifesting in other software (not Word, not Excel for example): my ppt is SLOW SLOW SLOW ! I am working in a very very simple presentation -- text only, black & white, no graphics, less than 15 pages -- and it takes at least 30 seconds to save, ages to open, ages to quit. I'm tired of watching that beach ball rotate !

Just noticed that for some reason it is also creating "temp" files -- "Powerpoint Temp, Powerpoint Temp 1", etc etc.

I run Software update automatically each week so should be up to date on all MS and Apple software. My 80G hard disk has 14G of free space, and I just ran "Terminal" earlier this week.