This trick might help since it works for me.
XL 2007 reference;
Here is a clip from there
To resolve this problem, follow these steps:
In Microsoft Office Excel 2007, click the Microsoft Office Button, and then
click Excel Options.
Click Advanced, and then click to clear the Ignore other applications check
box in the General area.
In Microsoft Office Excel 2003 or earlier versions of Excel click Options,
on the Tools menu.
Click the General tab.
Click to clear the Ignore other applications check box, and then click OK.
After you do this, you should be able to open workbooks by double-clicking