Reported cases of corrupted Datebook files are rare, but not unhead of. There are insufficient occurances or consistency to determine any cause. There really isn't anything we can determine from the corrupted file themselves, either.
Do back up your files regularly.
If you have experienced this kind of problem with one of the Palm applications on the Zoomer, please contact me directly. With enough details about the file and how the app was being used, we may find some consistency.
PalmTech