I fixed the problem!

I installed the SP1 for the user, and changed some code and it works!

In Mac the .RowSource property of combobox control is not supported!
The only way to add items is to use the AddItem method. The poor thing is that I need to hard code the items in the VBA code for simlicity. Rather than I can specify a range of cells and put it in the .RowSource property for Office XP/2003