This is a long-standing, extremely slippery issue that's exclusive to Windows.

The first time core images are loaded, they're processed into S3TC tiles at various zoom levels for use in the software. This can be quite slow, especially with many images. Thus the processed data are cached in Corelyzer's cache directory, which load very quickly in comparison.

However, sometimes Windows re-processes images that are already cached. I say "sometimes" because this behavior is difficult to consistently reproduce. Sometimes it happens, sometimes it doesn't. Attempts to reproduce the behavior in a Debug build have failed.

This is a serious problem for very large projects, which can take 30+ minutes to load if the cache is unused.