disappearing memo field text mystery

I am using Delphi 4 to write an application.  On the main form, there
is a Page control with Tabs. One of the tabs contains several memo
components, into which I have put a bunch of text via the memo
properties.  When I go to copy all my project files to another machine
which also has Delphi 4 installed, sometimes the text from 2 of the
memo boxes is gone!  I always copy *all* of the files in the project
directory, and delete all the old files in the other one first.  I
then have to enter the text in again (I cut and paste and put the text
on a floppy disk). This is really a mystery to me.  Anyone got any
ideas???

Thanks for any help
Clare