The Excel errors that cause COM Exception, can be resolved with the following steps:


Reason is: The Office message pump retrieves the message and dispatches it to a hidden OLE window where the call is unmarshalled and executed. However, before executing the call, COM first checks with Office to ensure that it is actually able to handle the call. In some cases, the call could result in an undesirable case of re-entrancy (such as when Office is in a modal state or it is in the middle of a long operation like a conversion). In those cases, Office can tell COM that it is too busy to handle the call, in which case RPC_E_CALL_REJECTED is returned to the caller. In your case, the failure is being converted by COM interop to an exception.

To overcome this, you will have to disable the COM Add-ins from Excel as follows:

(i) Click the File tab, click Options, and then click the Add-Ins category.
(ii) In the Manage box, click COM Add-ins, and then click Go.
(iii) The COM Add-Ins dialog box appears.
(iv) In the Add-Ins available box, clear all the check boxes and click OK.