There shouldn't be any (practical) upper limit on the size of file that you can create with Spreadsheet::WriteExcel::Big.

I've generated 50MB files and I know users who have created 100MB+ files.

I'd recommend a few things. The first is to check that you have OLE::Storage_Lite installed (it is required by ::Big but is an optional install) and that it is the latest version, 0.14.

The second is to remove Apache from the equation and see if the results are the same. For example, could you be hitting a timeout in Apache?

Also (perhaps this should have been the first) check your error logs and add 'fatalsToBrowser' if you are using CGI:

use CGI::Carp 'fatalsToBrowser';
[download]

--
John.