The $ icon applies the currency style to the selected cells.
One way to change what it does is to change the currency style.
Look under Format|Style...
Select Currency and change anything you want.
Note that these styles are workbook settings--each workbook saves its own
styles.
For that workbook (not worksheet??), maybe the currency style got deleted. You
can either create it manually (via format|style...)
or you could merge it from a workbook that has it the way you want. There's a
button inside Format|style that allows you to merge styles.
If you want this to change for each new workbook, you can modify the style in a
empty workbook and save that as book.xlt in your XLStart folder. (This is the
default template for new workbooks.)
