Label Wizard concatenation error

Access 2003, trying to use the Reports Wizard to create labels. When putting
any two fields on same line, the wizard does not complete the report and says
"The function you entered can't be used in this expression". Typically, two
fields are "First Name" and "Surname", but any fields results in same error.

It seems that the label in design view results in an unbound field. This
occurs only on the one new Windows Vista Business PC, yet not on a similar
install Windows XP Pro PC. VBA references are same, apart from "MS ADO Ext.
2.8 for DDL and Security" on the XP PC and "MS ADO Ext. 6.0 for DDL and
Security".

Have seen this question asked before, but have no solutions - stumped!
Joanne