VbaProject.OTM modules missing on opening OL2003

[Ken]

For the second day in a row, on starting up OL2003, SP2, a script that I've
created is missing--as in totally vanished.

I created a rule that runs a script on receiving messages that have an
attachment. The script is located in a module within "Project1
(VbaProject.OTM)".

The structure is:
Project1(VbaProject.OTM)
Microsoft Office Objects
This Outlook Session
Modules
Module 1
Module 2 (Module 2 has the
script)

(If the tabs or spacing of the above got messed up, it's meant to show that
the script in question is in Module 2. There's nothing in "This Outlook
Session")

The Rule/Script works fine during the day. I shut down Outlook at the end
of the day. This morning, for the second day in a row, when I started up
OL, I got a error message that the script did not exist. When I opened up
the Visual Basic Editor, the only thing there was the Microsoft Office
Objects branch (containing the empty This Outlook Session). There was no
"Modules" branch, and thus no Module 1 or Module 2.

Since I run Norton GoBack, I restored to a few hours earlier, and got it
back.

Any ideas what might be going on?

(Virus protection is up-to-date, FWIW).

Many thanks.

Ken