[vb 2005 expr] Error: Unable to cast COM object of type

The error that raises at runtime is:

Unable to cast COM object of type ‘System.__ComObject’ to interface type ‘NEROLib.NeroDrive’. This operation failed because the QueryInterface call on the COM component for the interface with IID

This happens when I try to execute a sub (that burns an iso DVD with data files) called by an asynchronous thread.

If the same sub is executed as click event of a button on the main form then there is no error and everything works fine.

Any hint or suggestion?
Thanks in advance!