After unticking Use Optimizer in the QODBC Setup screen I was asked for a user, left it at the default (current user), clicked OK and got the message

fqqbvsav.exe

The application has failed to start because the application configuration is incorrect. Reinstalling may fix this problem.

I reinstalled QODBC and got the above message after entering the CD key and user.  I removed QODBC and reinstalled from scratch but got the same error messages.

Before reinstallation I was able to read and write to Quick Books.  After installation I can read but have not tested the write capability.

Quick Books version: Premier 2007/08

Operating system: Windows Server 2003 R2

I'm not to sure what you mean by user here, normally the default is:

%UserProfile%\QODBC Driver for QuickBooks\Optimizer

which means the Windows user you're are logged in as at the moment. You should also be using a System DSN and not a user DSN.