CNVnator make histogram problem

[CNVboy]

I'm doing trio data analysis; so I merged those small root files into larger ones chromosome by chromosome. The merge process looks ok.

But when I tried to make histogram out of it, I got errors as below:

Calculating histogram with bin size of 100 for chromosome 'chr3' ...
Making directory bin_100 ...
Making GC histogram for 'chr3' ...
SysError in <TFile::Seek>: cannot seek to position -1646234942 in file NA12878_3.root, retpos=-1 (Invalid argument)
Error in <TFile::ReadBuffer>: error reading all requested bytes from file NA12878_3.root, got 0 of 1915944962
Error in <TKey::ReadFile>: Failed to read data.

What's the problem here?

thanks