Using Excel Report Writer to write multiple .xlsx files

Hi,

I got a very strange issue when I am using Excel Report Writer to write multiple .xlsx files in one protocol.
Basically, the 1st file can be generated correctly and can be opened without any problem. However the remaining file looks smaller than it supposed to be,
and throws error 'The converted failed to open the file' when I try to open it.

Attached is the example protocol and files generated.

I have tried both of the following environments, same problem.

Windows XP + Pipeline Pilot 7.5 + MS Office 2003
Windows 7 + Pipeline Pilot 8.0 + MS Office 2007

Any ideas? Thanks!