The first thing you can do is run Repair since it’s giving you an error message and shuts you out of  QuickBooks.

To Repair QuickBooks:

  1. Close out QuickBooks.
  2. On your keyboard, press Windows button and the letter E to open the Computer window.
    Note: in Windows 8, click the Computer tab.
  3. Click Uninstall or change […]

Resolution for 'Computer tabQuickBooks issue: 'Quickbooks 2011 will not let me export to an existing excel sheet – 2nd day the software shuts down and closes the file' available: Yes.

The Computer tabQuickBooks issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the Computer tabQuickBooks issue yourself by looking for a resolution described in the article. If it is a complex Computer tabQuickBooks issue or you are unable to solve the issue, you may contact us by clicking here or by using other Computer tabQuickBooks support options.

For more information about resolving issues related to Computer tabQuickBooks in Quickbooks/QBO or to get support for the issue 'Quickbooks 2011 will not let me export to an existing excel sheet – 2nd day the software shuts down and closes the file', click the link below: