Problem Deactivating Passolo 2011

I am trying to deactivate Passolo 2011 (Translator Edition SP8, version 11.8.9.153).

Passolo does not display any error message and appears to work properly. When I try to deactivate it by selecting

Help > About SDL Passolo...

I get to the "About SDL Passolo 2011" pane, where I find 3 tabs. When I select "License", the first item that appears is precisely "License: No license is found".

Thanks in advance,

Luis Marques