If you use Disc:Enhanced have you tried deleting the cache/page_enhanced/yoursite folder manually through FTP? the cache engine stores .old files so it can load old pages when rebuilding new ones. However it takes some time before those are removed so can create conflict with fragment cache. This is because the old cache files are loaded instead of the new ones.
Also if you use fragment cache on all pages its not recommended to use Disc:Enhanced since fragment cache with Disc:Enhanced prevents caching of pages.