Hi Leif,

You can try the below steps to solve this issue:

1. This can happen when the temporary version of a file is used, which happens when viewed from an email client or via a webpage due to restricted permissions. Which explains why copying it to your desktop works correctly as you are then accessing via standard permissions.
So, you have to:

Set component security settings back to the defaults:

1. Open Control Panel.
2. Open Administrative Tools.
3. Open Component Services and expand the tree under Console Root to Computers --> My Computer.
4. Right-click My Computer and select Properties.
5. Select the Default Properties tab and set the following values: Default Authentication Level: Connect, Default Impersonation Level: Identify

2. If you are using outlook as your email client, do the below steps: 

1. Open Excel.
2. Go to the File tab and select options.
3. Click on Trust Center and then the "Trust Center Settings..." button.
4. Select FIle Block Settings.
5. Click Restore Defaults.
6. Try opening an Excel Document from Outlook.

If that doesn't work, you can try this as well:

1. Open Excel.
2. Go to the File tab and select options.
3. Click on Trust Center and then the "Trust Center Settings..." button.
4. Select Protected View.
5. **Uncheck "Enable Protected View for Outlook attachments"**

Then try opening an Excel document that you can trust from Outlook and see what happens.

3. You can also delete your temporary files to see if it works:

Click on Start > All Programs > Accessories > Run,
type %temp%
Clear all the files from the temp folder and now try opening the attachment from the email.




I hope this helps.

Regards,
Lokesh

Which email program do you use? I would recommend setting up your email client.

Hi Leif. Sounds like you have done the appropriate steps (re-install the software). Can you tell me, the problem is limited to only a xls file, or are you having this problem with all Excel files? If there is only one file, it is very likely that the file is really damaged.