I've found this is usually a temporary issue because something got out of whack.
Look in your history panel and try clicking back several steps (click like 3-4 up from the bottom) and try again. If that doesn't work, go back further and try again. Restarting CH may help too. What I've found is that sometimes I do something that CH doesn't like (usually some numbers aren't lining up as it would expect) and see this, but it's usually easy enough to remedy. Let me know if that works.
I'm afraid none of that worked.
I even tried starting a new project in CH...I could import all the puppets I needed, but when it came to the background...
I guess there is something about the particular Ai file Ch does not like...is there a remedy for this? It worked in Ch Beta, but now doesn't like this one file.
Thanks for your help, Dave!
Does your AI file include a link to an EPS or TIFF file? If so, could you resave that linked file as an AI file and link to that version?
If that doesn't work, would it be possible to send us a shared link (via Dropbox, Google Drive, etc.) for that file so that we can diagnose the issue further? You can send it via direct message if needed. Thanks.