committed data being rolled back???

Has anyone experienced the following? The steps are:

1. Using Toad, issue an update statement.
2. Using same session in Toad, issue a commit statement.
3. Using a client program, view the updated records in a different session, verifying that the data did get updated and committed.
4. Time passes...
5. Client program no longer shows the data and neither does Toad.

Re-issuing the update and commit allows the data to be seen again (unless the phenomenon wipes the data again at some later point).

We have seen this happen multiple times with different updates, but can't find a pattern. It does not happen often. Most recently, it happened twice within a few days on the same updated data. The data was updated and committed and then the next day it was gone. It was updated and committed again on a Friday. On Monday, the data was gone again, requiring the update/commit to be issued again.

The fact that data can be seen in a different session means the commit had to have taken place. So what is reversing the update statement??

This is Toad "6.3.11.1 g" and Oracle 8i. Received on Mon Dec 16 2002 - 18:23:45 CST