Have you tried installing the most recent drivers/software for that particular keyboard? (Generally, a full uninstall of the software, then reinstall is best.)It should be available from the Logitech website:
Maybe at this link:
Software for Logitech
Using a Logitech "Internet Navigator" keyboard (corded)
it's 9 months old. It just started acting weird. When I use the word processor it misses almost every second letter sometimes 2 and 3 letters in a row. If I hit each key slowly and firmly it will register. The weird part is it's not happening now and it doesn't happen when using email. Only on the word processor. I have win98 and wordperfect.