Did you import the whole project or just the one job and corrupted the project? I've retro-imported jobs several times and as long as they didn't use functionality not available in the version to which I imported the jobs they worked fine (although often I'd get warnings during the import process). I do know that one needs to change some subtle keywords in the header so that the file format is recognized, I believe they changed one keyword in a line from singular to plural or vice-versa but you've probably seen that already.
Is it a server or a Parallel job and does it use uncommon stages?
No, I don't have a foolproof method and will keep your problems in mind next time I need to retrograde a job from 8.7 downwards. I had always assumed that if the job was imported it would work but that seems to no longer be true.
Trust me, it doesn't take much of a mistake to corrupt a project. Been there, done that, got the t-shirt.
In my case, it was a simple typo with regards to the category of the job which took the help of the awesome Karen Powers to resolve. Your issue may not have been any issue with the job itself but perhaps something in your replacement of the header itself. [shrug]
-craig
"You can never have too many knives" -- Logan Nine Fingers
I can't think of a software platform that allows one to go from a higher version of software to a lower vesion of the same software. There is a lot different between 7.5 and 8.7 that would perrclude a simple from this version to that version tool. You may be able to build a job in 7.5 and port it to 8.7, but I can't conceive that the other way would ever work.
Going backwards has never been supported, but usually worked when jobs didn't use features not present in the earlier version. Backwards compatibility has always worked and been supported; we could probably load V5 and earlier server jobs on 8.7 and they would work.
It does look like we've reached a version where changes to the .dsx have become significant enough to not enable this (unsupported) modification of .dsx headers to allow forwards compatibility.
p.s. Craig, Karen and I did ATS for UniVerse together for a while, we had our own office in Westboro. It was funny, people would be afraid to come in and talk to her or call her on the phone since she could be very acerbic with what she considered to be "silly questions"; but she really knew her stuff back then and has gotten even more knowledgeable over time. But she can still be very formidable (comes from being the only girl with something like 8 older brothers!).
p.p.s. Sorry for continuing the off-topic-ness of this but I always enjoyed talking to Karen and she liked the "interesting" problems I would send her way on occassion. And dang, she knew that sh...tuff inside and out, down all the way to the internals. If you get a chance Arnd, pass along a "hi" from me.
-craig
"You can never have too many knives" -- Logan Nine Fingers