Cell Format

There's a space in front of each of the numbers in Column F. That's breaking the calculation because it's multiplying a string by a number.

So how do I correct the problem?

You have to make sure the numbers in F get added without the space or go to each cell in column F and remove the extra space from in front of the numbers.

Either do a search/replace for the space character

or use a formula like this

=E2*SUBSTITUTE(F2,CHAR(160),"")

To do a search/replace

Select the character in the cell. (You would have to do this because the space is not a normal space) and then paste it in the search box.

The nub of the problem is that the formula does arithmetic when the cells are formatted as text, even though they contain numbers.

It is easy to set the format of cells to text, but there is no obvious way to reverse the process. You have used one way, but that would be tedious if you have more than your six cells to do.

Microsoft has an article here:
http://support.microsoft.com/kb/291047

It lists seven methods, including the one that you used. I think this would be the quickest in your case

"Use the Text to Columns Command
This method works best if the data is arranged in a single column. The following example assumes that the data is in column A and starts in row 1 ($A$1). To use this example, follow these steps:

    Select one column of cells that contain the text.
    On the Data menu or ribbon, click Text to Columns.
    Under Original data type, click Delimited, and click Next.
    Under Delimiters, click to select the Tab check box, and click Next.
    Under Column data format, click General.
    Click Advanced and make any appropriate settings for the Decimal separator and Thousands separator. Click OK.
    Click Finish."