When v2006 first came out there was an increase in the variable name length limit from 7 to 12. In v2006.1.43, this was increased to 60. I'm guessing that's what's going on here given that you were using v2006.1.31 *and* the variable name length increased from 12 to 13 when the problem started to occur in your data. When we bumped the limit up to 60 I believe we also fixed an associated bug that may have been responsible here. Try updating (it's free) to the final release of v2006 (v2006.2.40) or upgrade to v2008 and either of those ought to resolve the issue. Note that the final release of v2006 is still available here: www.empirisoft.com/download_old.aspx.