I was upgrading from SS 2.3.3 to 2.4.1 and replaced DOM, SWF and image gallery modules to most recent versions on my localhost installation (running SS on xampp for windows). If its important, i replaced them all in one go - SS files and the modules.
Upon dev/build?flush=1, i got this message:
Fatal error: Class 'DataObjectDecorator' not found in D:\xampp\htdocs\ztm\dataobject_manager\code\AssetManagerFolder.php on line 4
yes, i doublechecked and removed sapphire, cms and googlesitemaps and removed jsparty.
the modules installed (all updated to newest available from silverstripe.org/modules/ are:
+ two own modules, which dont use that extraDBFields() method
SOLVED: I had extraDBFields method in BlogEntryDecorator I have created in order to extend Blogentry.