I am a designer who is having the same issue. Since upgrading to InDesign/InCopy CS4 this issue has appeared in the Assignment files I send to my remote client on a PC.
I noticed that in the InCopy Assignments, looking at the Links panel shows there are a number of images that have broken links, with the letters 'DT' to the right. DT indicates 'Deleted text in a tracked change'. Information on tracked changes is minimal in the Help Menu.
I believe that this is happening because I am building from an older document that had links to a previous Assignment. Apparently my InDesign document has kept track of images that were embedded in deleted text.
I managed to reduce the issue by recreating all of the text frames from scratch. But every once and a while it would resurface, seriously slowing down our workflow.
I'm hoping to find out more from the community so that next time we produce this publication there are no snippet snags.
To follow up to SMonsen, I am in a similar situation in that I have to get my 88-page catalog in working order right away before the next production cycle starts.
So, I've been trying everything to fix one of the many problematic InCopy Assignments from the last painful round of production, and I've stumbled upon a workaround.
Before I mention it, I think the most effective workaround is to go back to an all CS3 workflow. I think the source of the issue is with how InDesign CS4 exports for InCopy, whether it be for InCopy CS3 or CS4.
The other workaround I mentioned is to cut and paste all of the content of your current 'infected' document and paste it into a fresh new document.
Doing this fixed another issue I had with hyphenation settings not being preserved and it also cut the 'import snippet' time to a manageable wait.
I think InCopy CS4 always says 'importing snippet' at some point, but for certain files it takes forever to do. In my testing it will always eventually open, but 10+ minutes is too much time to wait.
I too am having problems with .icap files. When I try to export a chapter to an icap, the file is 112MB which is way too big to email.
In my experience, no one checks the InCopy user forum. If you're still having problems, I'd suggested posting it in the InDesign forum. That's what I'm going to do!
Good luck, guys!
If you use dropbox then you don't need to do the icap thing (Package for InCopy). Your remote users can just open the layout and/or assignments from their local dropbox folder. I have a couple publishing clients using it, so far so good! http://getdropbox.com
BTW there's nothing significant about the "import snippet" message ... everything in ID/IC is a series of snippets, internally. ;-) I wish Adobe wouldn't include it in the alert.