ITouch calendar is deleting older dates

[Beach004]

When I got my iTouch several years ago, I imported into it all my Palm calendar entries, some dating back to the early 1990's. It was a chore, but I figured it out, and there have been no problems; I can look back and there they are. But last week I discovered that all the iTouch calendar entries before Aug. 25, 2009, have disappeared! If I look at Yahoo calendar, which is synced to the iTouch, the entries are still there; and entries created in other calendars than iTouch for dates before 2009, are still visible on the iTouch calendar screen; it's only the iTouch entries that have vanished.

Here's more: If I create a new entry for August 29, 2009, say, in the iTouch calendar, it works; it's there and it stays there. But if I create it instead for August 22, 2009, then it appears, but in a minute or so it vanishes--even though I can still see it on the Yahoo calendar.

I know this sounds crazy; but it's making ME crazy. Any ideas?
Beach004