Hello,
I was not able to replicate the issue at my end with the latest version of C1TrueDBGrid i.e. v4.0.20133.61336. C1TrueDBGrid was bound to a stored procedure in SQL Database at design time. Later, the grid designer was used to set the NumberFormat of a numeric column to "####" and it correctly displayed all the cells with value 0 as blank cells.
I would suggest you to test the issue with the latest version of C1TrueDBGrid which you can download from the following link: http://prerelease.componentone.com/dotnet40/C1TrueDBGrid/2013-T3/
Hope it helps.
Thanks,
Manpreet Kaur