I've not encountered one, and I've had to edit large background graphics (1024x768) and tend to import them back in as BMP (the wisdom of doing that as opposed to JPG or PNG can be debated).

Just note, everything you add to your CP project makes it larger - and including audio and custom images will probably have the biggest effect...so as always, just keep your images as small as possible (in size and dimension).

CP can scale quality images pretty well, so there's a tempation to bring in large and scale down. I'd avoid that where possible.

But all that said, I dont't recall CP ever preventing me from importing an image because the file size was too big...but I've never tried to really push it either...

Captivate seems to 'remember' assets that were deleted sometimes, resulting if files that are larger than they should be...and are often fixed by the copy/paste method you've read about - and that's not guaranteed to work, as you've found. It would be nice if there was a more official 'save and compact' feature as there is/was with other products.

Be sure to click the 'find unused objects' button in the library - finding and removing those unused items, then at least doing a 'save as' can help reduce file size by alot.

You can set the recording properties of the files you record into Captivate, but that's not as critical as the format you publish to. Look for those audio publish settings. If it's just narration, you can probably reduce the default quality a bit to save published size...

Images, you can do the same...reducing the published quality. But you'll almost always surely get better results if you optimize images outside CP...

HTH!