Is it something in your data thats being inteprepted incorrectly? Are you dumping blobs as well? Can you see the \N in the file?
If your not dumping blobs you might also want to try a different --format.
I did an upgrade from 7.3 to 7.4 by dumping plaintext in 7.3 then upgrading to 7.4 and importing and that worked fine (it wasn't an OpenACS instance tho).
You might also want to try two dumps one for data (-a) and one for schema (-s) to see if you can narrow it down.
- Steve
