A Haunted Database

Here's a mystery I hope someone can solve for me.

We are entering blocks of HTML into a table called bodyparts. We use PHP3 to
break up these blocks into several chunks to keep the length below the
maximum. When the end user calls up the section, the "bodyparts" are
extracted and re-assembled.

The output pages work fine . . . for a while. We set up the output pages
during the day, check them for accuracy and go to bed thinking we have done
a great job. Then , in the middle of the night, something happens and when
we awake, we find the HTML has been scrambled like so many breakfast eggs.
Not all sections are scrambled. In fact it is the same sections every single
time. So we re-enter the data, check it, assume we are done, and then the
same thing happens the next day.

To gather some empirical evidence, I ran pg_dump at 7pm on the offending
table. I check the output pages at midnight the same evening, and they all
were good. When I got back in front of the computer at 9am, the pages were
scrambled again. I ran pg_dump a second time to a separate file. The file
sizes were different (insert scary music here). No one had touched the
database or the pages.

I reloaded the data and everything is back to normal. But I suspect it will
happen again tonight and I am afraid. Does anyone know what inhuman entity
might be causing this to occur?