Some customers have reported these kind of errors either when editing a part family spreadsheet or accessing the Modeling spreadheet.
The 1st error is immediately reported to the user as soon as Excel is called, the 2nd error is usually reported within the NX syslog.
Some cases in the past were sorted out by adding and enabling the relevant ug.xla add-in. in the Excel options
or by uninstalling the Foxit Reader program (severe conflicts with this application are known).
However for some customers this might not help (and many customers haven't got Foxit Reader installed).
A customer of ours was able to work out this annoying problem by adding the main UGII folder to the list of Trusted Locations within the Excel Trust Center.
While this is not necessary in all cases it might help and actually was conclusive in the mentioned user case.
OS Version: 764SP1