forums.wsusoffline.net

Something went wrong. A previously downloaded file failed verification,
and re-running didn't help.

No documentation on what to do in this case.

I tried deleting this file, but that seems to have made the problem
worse, now the update process fails a little sooner.

Is there some better alternative to starting over from scratch?

Actually there is documentation. Unfortunately few people read FAQs.

From the faq-enu.txt included with the package (online: http://trac.wsusoffline.net/browser/tru ... aq-enu.txt)

FAQ wrote:Q: During download, I receive a file integrity verification failure. What can I do to resolve this?
A: If you're sure that the patch files in your repository weren't manipulated, you may delete the corresponding checksum files under ...\client\md. They'll then be recreated during the next download run.

Thanks, I missed this in the faq, but will try it if it happens again.

It happened again, for no apparent reason, & deleting the hashes is not sufficient.
I get this error now:
Verifying digital file signatures of Windows Update Agent installation and catalog files...
Warning: Deleted unsigned file "G:\wsusoffline\client\wsus\wsusscn2.cab".

ERROR: File signature verification failure.

Is there something else I can do?

Deleting the hash should be sufficient, but you may be getting the same damaged wsusscn2.cab again if your computer delivers a cached file. Try again after clearing your IE cache.

Btw. does it break download at or near the 20,000,000 Bytes mark?

And please take a look at this thread, whether you have installed KB2524375.