Attempted to read or write protected memory issue

I get the following error message when trying to write/read to a Data Acquisition Switch Unit 34970A using IEEE.

Attempted to read or write protected memory issue. This is often an indication that other memory is corrupt.

Originally the application was written in VB6, but I migrated to VB.Net 2008, that's when the problem started. I'm using vbsicl32.dll and I had to change some variables declarations as they were no longer supported in VB.Net 2008, such as "Variant" to "Object"

I'll appreciate any help on this issue.