I am using Excel 2004 for Mac Version 11.2 on Mac OS X 10.4 (Tiger) right now.
I cannot for the life of me figure out why it insists on using commas to represent decimal places. Does anyone know how to change this to periods?
Look up in the menu bar, and make sure the country selected is correct for you ( Assuming US ). If it's set for a different country, you may see this issue. I believe if your input is set to German, for example, it will exhibit what you describe seeing in Excel.
EDIT: details on solution from @sixtyfootersdude:
This is what my international panel looks like. You can see that there is a little warning there. Here is what resolved the problem:
Apparently this solves the problem.