After installing Lync 2010 the TAPI calling feature in Outlook 2010 no longer was working. It seems that Outlook uses Lync as it’s default “Call Contact” method.
To change this you need to override this setting in the registry with the following key (you can paste this to a “.reg” file and double click it to add it to the registry):
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Outlook\Call Integration]
"TAPIOVERRIDE"=dword:00000001
