All action took place on a iMac with MacOS/X 10.5.7.

Here the receipt to provoke the error:
<verbatim>
wget
mkdir bug
cd bug
fossil new repos.fsl
fossil open repos.fsl
unzip ../t3xr2.zip
fossil add .
fossil com -nosign -m "Import failed"
</verbatim>
Fossil will answer with:
<verbatim>
New_Version:
fossil: tree checksums before and after commit do not match
</verbatim>

Please let me know, if you need further information or if I can help somehow ...

Thanks,
:-)