Is write caching disabled on all HDD in the system?

>I've been getting the following error message every day or so:
>
>Memo File (Form-Name).SCT is missing or invalid.
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>This occurs after I have been working on a form, when I try to save it. It's not the same form every time or anything, so I can see no pattern.
>
>Now, obviously, the SCT had to exist when I opened the form to edit it, and I can see that it exists, so it must have become invalid.
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>How can that happen, if I am saving it???