Good news and bad news. The bad news is that you are getting this error because CVI 6.0 doesn't support 64-bit integers. There is no great way around this unfortunately without quite a bit of effort on your part.
The good news, is that the new version of CVI, 7.0 just released last week, now supports 64-bit integers. It is also include a ton of great improvements to the development environment that are well worth the upgrade. To see more about the new version of CVI you can go
here and select Learn about LabWindows/CVI 7.0. You can upgrade your version at
http://www.ni.com/upgrade.
Best Regards,
Chris Matthews
National Instruments