UIImage not appearing when cached

I've got a UITableView that's loading a bunch of RSS feeds, and the favicon for each feed is shown in the table cell. It works well most of the time, but sometimes the image does not appear. Looking through the debugger, the images that don't appear have the NAMED and CACHED flags set to TRUE, with all the other flags set to FALSE. Images that have all all the flags FALSE will appear correctly. Elsewhere in the app, (in different TableViews) the favicons that aren't appearing will appear correctly.

Does anyone know what's going on, or how I can proceed debugging? I've drilled down to the flags...not sure where to go from here.

If it makes a difference, I'm also creating these images with 开发者_运维百科initWithData, not imageNamed.

---

OK, I've looked into this, it has nothing to do with the caching. My code was loading an image that has no content, and that's why I couldn't see it.