Strange problem..
Site is on 2013 (it is hosted in Office 365) and the user is running IE9. Just recently updated from IE8 where there was no problem.
The issue is when she browses to an Excel document on the site and then clicks "Edit Workbook" and then "Edit in Excel" - the window stating "We're opening your workbook in Microsoft Excel..." appears, but it never actually launches Excel. She can then click on "Edit in Excel Online" and it works, but she prefers to work out of the Excel client.
IF she has the foresight to click the "..." on the document and chooses the option to Edit from there, the site launches Excel and she is able to work as expected.
She has tried on multiple documents as well as on a document in her OneDrive. All behave the same.
I am able to launch this (also IE9 on a machine) without issue. She is able to launch in Firefox/Chrome and it works. Editing it online is just fine too, no matter which browser. We updated the Office install to the latest version.
So the only trouble seems to be IE9, her machine, clicking the edit in excel option after you have opened up the work book. The IE9 settings should be pretty standard for our company's build so why her machine is not working is not clear.
Any ideas on what to check or change?