Cannot open spreadsheet

I cannot open a spreadsheet from an e-mail attachment, from a hyperlink or
from Windows Explorer. Excel opens and the blue screen indicates "ready" but
the file won't open.

The "Ignore other applications" option is not checked. Sometimes I can get
the file to appear on the screen if I click off Excel to another program
window, then click back. That doesn't always work, but usually does.

I've searched the previous posts and have tried unchecking ignore other
applications and excel.exe /regserver sequence. Neither are working. Oh,
running Windows XP Professional and Excel 2007.

Thanks,
Katherine