Byte count too large error while copying histogram

[Wile_E_Coyote]

Maybe you are facing this bug (check which ROOT versions produced your files, which versions you use to read them, and do not use the versions known to be broken):

Cannot write histograms in the file because of opening another root file

The version affected are: v6.14/00, v6.14/02, v6.14/04, v6.14/06, v6.14/08, v6.16/00 The tip of the patch branch v6.14 and v6.16 and the version v6.18/00 and later are not affected The problem is due to commit 8c9c1a3fbe3a1c5704635f8941abeb9596104c77 (Change to onfile format without a class version upgrade). And yes this means we need to tag v6.14 and v6.16 very soon.