Highlights Jumping in Win Explorer (98)

In Windows Explorer (Win 98), I select a folder in the left window and the folder name is highlighted. When I then select another folder instead, the newly selected folder name is highlighted, then the highlight jumps back to the previous folder, then back to the second folder again, then the folder opens. The folder does open OK after the highlight jumps back and forth. I’m not sure when this started but noticed it a short time after installing new RAM and a program or two. Any advice? Isthis just Win 98 being ‘unstable’ and my only solution is to reinstall? This problem does not exist in the right window.