Hi, just debug it. I guess some primitive returns false instead of the basic filesize. There is AbstractFileReference>>humanReadableSize looking like this: humanReadableSize ^self size humanReadableSIByteSize So if size returns "false" then you will get this error. If you trace further you may end up in DiskStore>>basicSize: anEntry which gives the 5th entry. Just check where it is coming from (somewhere in FilePluginPrims I guess). Maybe the size is so large that it fit's Smalltalk but not C. But I just guess, try to debug. Bye T.