CS4 does not open jpegs it generated itself

Question

I have just spent half a day preparing jpegs from hires psd's, and I have just found out that the jpegs are all corrupt. When I try to open them, I get a warning message:
Could not complete your request because an unknown or invalid jpeg marker type is found.
I have the same workflow for years now and have never had this happen. When I upload the jpegs to a website, they are all black. However, when I open them in Preview, they do open.
Any idea how this can suddenly happen? I do this work every day, so I'm both puzzled and concerned.
Any help or advice will be greatly appreciated.
I work on a MacPro, MacOs 10.5.6

Answer 1

This is the boilerplate text I use in connection to saving to a network (please NOTE the part where it explains that normally, it does work, but that it is impossible to troubleshoot someone else's network remotely, and that's why it's not supported by Adobe):
If you are opening files over a network or saving them to a network server, please
cease and desist immediately
in the event you are currently experiencing problems with one or more files.
Working across a network is not supported.
See:
http://www.adobe.com/support/techdocs/322391.html
Copy the
CLOSED file from your server to your local hard disk, work on it, save it again to your local hard disk, close it, and copy the closed file back to the server.
Of course, the fact that Adobe does not support working across a network does not necessarily mean it won't work. It should.
Adobe's position is that there are too many variables in a network environment for them to guarantee that everything will work correctly in every network, especially given the fact that if something does
not work properly, it's probably the network's fault, and Adobe has no way of troubleshooting your network.
If you can't work locally, you are on your own, and if something happens, you're on your own. If you must work from a server, make sure your network administrator is a competent professional.
When problems arise, a lot of valuable work can be lost.