Numbers in excel cell disappear after typing

Hello,

I am trying to use an external number pad on my macbook to enter data in excel. The number pad works in all applications, including word and open office spreadsheet, but not in excel. When I type a number into a cell, it appears briefly in the formula bar and the disappears. If I move the cursor to the formula bar and type it works, but this is of course would be very slow to do. Any ideas why this may be occurring? The fact that the number pad works in all other programs leads me to believe it is some sort of setting within excel that I need to change. Any suggestions will be greatly appreciated.

Thank you

From what you said I believe it's possible that the format is not visible. E.g.: white background, white letters, or the number format is such it hides what you type. (Put it to general to make sure it's normal.)

No, it is only numbers entered using a usb number pad. If I use the keys on the laptop everything works fine. However, when I use the number pad the number appears for a split second and then goes away. If I type a number and then very quickly press enter, the number will stick. Again, the number pad works perfectly in all other programs. It's a rather strange behavior.

No, it still does not work. The number appears briefly and then goes away. I have tried the number pad on two other computers (both macs, one with office 2008 and one with 2011), and the same problem occurs. Works in all other programs, including other office programs.

The -/*+ characters all work perfectly (as well as the enter key), it is just the numbers and the period key that are not working with excel. Num Lock is turned on on the number pad. The brand is a cubeternet. The packaging says it is compatible for mac and windows.